A/N: So, this is my first attempt at a Bleach/HP crossover. I hope that I won't disappoint all of you. Here is some basic background on when this will take place, who the characters will be, etc, etc...

-Takes place after Aizen first betrays the soul society, so there will be spoilers up to that point, and perhaps some spoilers about character personalities and backgrounds from all over the entire series.

-Rukia is able to use her Zanpakuto, and Ichigo has gained control over his hollow powers

-For Harry Potter this is happening during the Order of the Phoenix

-Bleach knowledge is necessary, Harry Potter knowledge not so much since the main character will be figuring it out as well so you can just follow along with him

-main character will be Toshiro Hitsugaya

-for Bleach terms I will be using both the Japanese and English terms, sorry if this confuses anyone

-The Diamond Dust rebellion has happened, but it will not be a major part in the story

-There were major spoilers for all of the Harry Potter series and all of the Bleach anime (up until when Aizen is finally defeated)

Story summary: Aizen targets Hogwarts in hopes of using the wizard's knowledge of magic to aid him in defeating the Sol Society. Captain Hitsugaya Toshiro is sent to eliminate the Aizen threat, and to aid the Order in defeating Lord Voldemort so that he won't pose a threat to the Soul Society either.

Chapter One- An Unexpected Irritation

Hitsugaya POV

I was walking through the division barracks, searching for the 'elusive' Matsumoto. Then again, she's always 'elusive' when there's work she has to do. If there was one good thing about my Lieutenant it was that she was a predictable person. Despite that fact though, I swear that if I find out that she's been drinking again I'll freeze her ass to the chair as soon as I catch her and refuse to let her get up until she's done all her work.

Eh, who am I kidding? I won't be using Hyorinmaru to freeze her to the chair. It'll go the same way it always does; I'll yell at her a bit, get her to fill out a few sheets for me, and the end up repeating the process when she finds some lame excuse to run away. That, or I'll leave for a few seconds to grab something and return to find out that in the five minutes I was away she had managed to get herself drunk and fall asleep on the couch.

Sometimes I really, really want to transfer my Lieutenant to a different squad. Every once in a while I'll go so far as to pick up the transfer forms, figuring that Captain Kyoraku wouldn't mind having Matsumoto in his squad (hell, the guy would probably worship me for putting someone with assets as huge as Matsumoto's in his squad). But then Matsumoto would do something truly amazing, or I'd remember all the things we'd been through together or she's do something particularly stupid just to try and cheer me up and I'd end up throwing the papers right back into the garbage bin with a guilty feeling.

Not to mention how utterly terrifying it is to think about how much trouble Kyoraku and Matsumoto could get into without anyone to rein them in.

Oh well, I guess I'm stuck with a drunken, partying Lieutenant until the day I die. It could be worse I suppose, I could have Yachiru as my Lieutenant. Isn't that a scary thought?

Eventually I felt a trace of her reiatsu coming from the top of the Sokyoku Hill. The first thought that popped into my mind was, 'What the hell is she doing up there?', the second though was, 'damn... I'm going to have to climb all the way up there.'

Climbing the hill wasn't that much of a chore for someone who knew shunpo, I could basically jump up there in a few minutes, but it was still rather irritating. At least I'll get to train shunpo for a bit to get up there. I've been so busy lately that I haven't had the time. Not only that, but my reiatsu was starting to build up because I hadn't released enough of it in training. If I don't train soon and let some out then it's all going to come bursting out, and that's going to suck for the weather patterns in the soul society.

Eventually I managed to get to the top, and I was completely and utterly surprised when I got there.

I had expected to find her and a couple of other Lieutenants having a secret drinking party, or all of them passed out in a heap. Instead I found Matsumoto helping a couple of the newer recruits master some of the higher level kido spells. To say I was shocked that she was doing something that productive would be putting it mildly.

"Matsumoto-" I said, intending to tell her good work.

She cut me off, "Oh... Taicho! I'm so sorry, I know I should be doing paperwork right now instead of this, but they asked and I couldn't turn them down. They all just wanted to learn something new and train, I'll come back immediately if that's what you-"

Matsumoto was then cut off by a man- his name was Kinsai, I believe- "Greatest apologies, Hitsugaya-Taicho, but don't blame her. We asked her to help up." Everyone else nodded.

I sighed, shaking my head as a smile started coming onto my face, this was the most work I'd seen Matsumoto do in ages- why would I stop her now? "Relax, I'm not mad. I just wanted to know where you all went to. If you want to train then just tell me so I won't have to come and find you. As long as I'm here though I might as well stick around- anyone want some help with training anything? You'll be able to actually fire shots at me, and I'll be able to tell you how effective they are."

A couple of the squad members got huge, broad grins. I could tell that up until now they had been training on targets. Though effective, it was nowhere near as fun as getting to fire at a real person- especially when that person happened to be a superior who you know you can't hurt.

Matsumoto shot me a relieved look. If I had to guess then I would say that this group had asked if they could train on each other earlier, and she had said no, fearing that they didn't have the training yet to do so without causing bodily harm to each other.

I spent the perfect afternoon training with them, helping build up several things including their kido abilities, squad moral, and trust in their Captain and Lieutenant. Not to mention it helped to take away some of my ever-building reiatsu, which had been starting to get distinctly uncomfortable.

It wasn't going to be a long lasting solution- for that I needed to go train with Hyorinmaru tonight, just for a few hours on my own with no one around me so as not to freeze anyone solid. I heard Hyorinmaru growl approvingly in the back of my mind; he wanted to train, to soar in the sky with thoughts of battle in his mind.

All of the trainees called it quits, agreeing to mutual exhaustion. They started to make their way back to the Squad Ten barracks, me with them, when a Hell Butterfly appeared. Matsumoto held up her hand and it landed, reading off the message she said, "Soutaicho requests a meeting with you."

I nodded, speaking lower so the subordinates wouldn't hear I said, "You will finish your paperwork when you get back- won't you?" my voice became as threatening as I could make it and she gulped.

Matsumoto nodded, she would have felt my reiatsu. "Of course, Taicho." she sighed, "But it's going to take me ages to do all of it though." she whined.

"I didn't say you had to do all of it, I'll finish the rest of it when I get back, just work until I get there and we'll swap so you can go out. You did good work today." I was hoping if I tried a new technique and tried guilting her into it by being nice then maybe she would actually do some of it, as opposed to none of it.

"Oh- thank-you, Taicho! I'll get right on it!" she sped off down the hill using her shunpo.

I frowned; either that strategy just worked really well, or it worked really, really badly. I shrugged, Matsumoto was who she was. She's a big girl who can take care of herself. If she doesn't do it then I'll chew her out later.

I sped off towards the Head Captain's office.

Walking through the First Division's barracks I was once again envious of the facilities they had here; five training rooms, a couple of squad four healers posted here permanently, their own mess hall. And all inside one building, no need to go outside if it was raining. If our squad had training facilities as nice as theirs then we wouldn't be training at execution central using wooden targets that had to be replaced every two shots. It was beyond irritating how they got all the money because Old Man Yamamoto was in charge.

The door to his office (his huge, way, way overdone office) was open so I let myself in. Old Man Yamamoto was standing against the railing with another silver haired man.

The man wore the longest, most obscenely purple robes I had ever seen. They reached to his feet, and were just short enough to show a pair of worn loafers and bright green socks. He turned to look at me and I saw a pair of bright blue eyes twinkling behind a pair of half-moon glasses. His beard nearly reached his knees. Overall, he was a tall skinny old guy. I could've sworn I had seen him before, but that could just be the fact that he bore a striking resemblance to Yamamoto.

"I have a new assignment for you, Hitsugaya-Taicho." said head Captain Yamamoto, "There has been a disturbance in the world of the living that I wish for you to go deal with."

I nodded, allowing him to continue, "This man here is Albus Dumbledore, headmaster for Hogwarts school of witchcraft and wizardry." he introduced.

The blank expression on my face must have told him that all that was completely meaningless to me. "Wizards and Witches are a species of human similar to the Bount and Quincy. They are able to perform acts of magic by channelling the power from their wands, which contain powerful objects such as phoenix feathers and dragon heartstrings."

I felt Hyorinmaru growl disapprovingly at that last part, he didn't want to know how the wizards got dragon heartstrings.

"Because of this they have a vast knowledge of fighting and technology using magic stored there, we feel Aizen may be attempting to break in and take over Hogwarts. I will be sending you there so that you can pose as a student and stop Aizen."

My eyebrow twitched. I was insulted that they wanted to go to this school as a student. The temperature in the room accidently dropped several degrees. As angry as I was though, I didn't complain - I would do anything to get my hands around Aizen's evil, traitorous neck so I could beat him senseless for hurting Momo.

"There is another problem at hand too, a dark wizard known as Voldemort. In his wish for immortality he has not only destroyed his own soul by splitting it seven times, but he has also damaged many innocent souls as well. He must be stopped and eliminated. That is all, Captain, I will see you at the Senkaimon in two hours. I trust you will be there in time."

"Hai," I said, bowing and leaving the room.

Damn, looks like I need to work fast.

I quickly sprinted as far away from the Seititei as I could, going into a remote forest and using shunpo so much that I burned off huge amounts of spirit energy recklessly. I needed to lower my power completely before they put the power seal on me for my mission, and I was going to have to do it fast. Normally I would have started off training with some low level kido and sword work, working my way up to my shikai and then my bankai.

I just didn't have the time for that right now.

"Bankai!" I yelled, and Hyorinmaru flared up inside of me with a satisfied roar. I felt my wings and tail grow out, fusing with my skin and becoming part of my body. Having ice become part of my body wasn't unnatural for me. It was how it should be, Hyorinmaru was another part of me- completely made of ice- and I trusted him absolutely. This form, though difficult to hold onto, was natural for us.

I spent a very satisfying twenty minutes, sending ice dragons flying and letting all my rage out about this stupid, degrading and completely useless mission. By the time I was done, all that was left of the part of the forest I was in was a huge crater filled with shattered ice and snow. Hyorinmaru growled with satisfaction as I let my bankai go.

Good work, that type of training is necessary too you know. In your regular training you hold back, but let's face it, you never do that in a fight. In a real battle you let all your power out so you can shatter your enemy in one fell blow.

I suppose you're right. I agreed, looking down at the destruction below me and turning to leave the forest. But I also need to know how to preserve my strength- that method burned off almost all my energy in under twenty minutes.

Also true, Master.

I used shunpo to get back to the office, where I was surprised to find Rangikou doing paperwork. Shit, she's never going to let me live it down now that I'm the one not getting my work complete and she is.

"Matsumoto, I apologize, but I've been sent to the world of the living on a yearlong mission. I'll get Ukitake to help you out, okay?"

Matsumoto got a kind of upset look on her face, I assumed it was because of her paperwork, but then she jumped on me, giving me a hug and smothering me with her boobs of doom.

"Oh, Taicho, I'm gonna miss you so much!"

I tried to fight her off, but she had my arms pinned and I couldn't get a good kick in from this range without hurting her.

"I can't believe you're getting sent there on such short notice! Oh, make sure you write every day. I'm going to be so worried about you.

I. Can't. Breath.

"Imagine how upset everyone will be now that you're gone. What am I going to do without you?"

I managed to get my legs up and braced against her stomach to give me some leverage. I started pushing myself away from her until her arms released with a snap and we both flew backwards, me going and slamming into the desk while she rammed into the couch.

"Taaaaaiiiiiiiiiiichoooooo... that was mean." she whined.

"Then you shouldn't have jumped on me." I said, gasping to catch my air again.

"I'm going to miss you." she sniffed, her eyes starting to mist.

"Yes, you've said that already." I said coldly.

"You don't have to be so cold."

"There are two schools of thought on that one."

She looked like she was going to jump me again, so I quickly said, "I have to run out to get some stuff and set some things up for you. I'll be back as soon as I can to help you do the paperwork. Stay right here, you're almost done!" I took off through the door, using shunpo to jump over a few roofs and get to the squad twelve barracks in less than twelve seconds.

I stopped outside of the barracks, and suddenly Hyorinmaru burst into a huge fit of raucous laughter. You've been awfully quiet today. I informed him, wondering what my usually talkative Zanpakuto had been thinking about.

I just wanted to see how today played out, I have to admit though, even I'm not stoic enough to not laugh at the things going through your mind when your little Lieutenant jumped you.

You call Matsumoto little?

Well some parts of her are, some parts... aren't.

That's one way of putting it, I suppose.

The door to the barracks opened and Hyorinmaru fell silent as I walked inside. This place gives me the creeps, he muttered and I agreed. You have no idea how many times the Captain of squad twelve has tried to knock me unconscious and drag me off for testing. It's bloody annoying that I have to constantly look over my shoulder.

Captain Kurotsuchi was not a man who I would call sane. He was a complete and total psychopath and his treatment of his daughter only served to prove that. Everyone was a test to him, me, her, he would probably perform tests on the head Captain too. There were days when I wanted him to try to drug Yamamoto up so I could kill him. If there was one guy who I would murder (excluding Aizen, Gin, etc.) then it would be this man. He was warped beyond all recognition.

"Why, Hitsugaya-Taicho. What a pleasant surprise." he leered creepily.

"Kurotsuchi-Taicho. I would like to retrieve all the things I need for my mission. I assume you have been informed?"

He nodded, but from the pinched look on his face I would guess that he hadn't been told. He walked over to a wall and grabbed a Soul Phone, some Soul candies and the spirit ink that he would draw the power seal with. I hated being at twenty percent, not because of the lack of power itself but because in order to get the tattoo on I had to let Kurotsuchi get in my personal space and draw it on. Last time he tried to secretly jab me with some needle while he was doing it, and I still don't know what kind of solution was in there. Just to be careful I let Hyorinmaru put a sheet of ice over my entire lower body and arms that were covered by my clothing, Kurotsuchi couldn't see it and be insulted, but if he tried to jab me then it wouldn't get to my skin... I hope.

He quickly and efficiently drew the seal on me while I resisted the urge to draw Hyorinmaru on him.

He only tried to drug me twice, which is definitely an improvement over last time. Eventually I was done and I got out of there as quickly as I could without appearing to turn and run away. I had to go to Ukitake's office now; I hoped he wouldn't be sleeping.

He wasn't, luckily, and I walked inside to find him reading a book. He looked up and said, "Toshiro- what a surprise. Can I help you with anything?"

Ukitake Jushiro was one of the few people who could get away with calling me by Toshiro, I had a great deal of respect for him and I liked to think our relationship came something close to friendship. "I have to go away on a mission for a year, it was sudden and I didn't have time to prepare things for Matsumoto. I was wondering is maybe you could keep an eye on her. I don't mean spend any of your time doing her work or anything, I just mean if she has a question if you could try and answer it for her since I'm not available."

"Of course, Toshiro. Matsumoto is quite capable though, I doubt I'll have to help her at all. Where are you going?" he asked.

I know it was probably meant to be a secret mission since it was sprung on me so quickly, but I figured no one was going to mind if Ukitake knew. I poured out the entire thing to him, from the hard details to my irritation at having to pretend to be a student.

He nodded at the end of it, "Don't worry. Besides, this magic stuff could make for a brand new fighting style. You'll teach me some when you get back- right?"

I nodded, happy at the idea of being the first Shinigami to master something and happy that he had asked me to teach him, "If I can. I have no idea how it works."

Ukitake smiled, "My thanks, now..." he began shuffling around in his desk, "I was planning to give you these after the Captain's meeting tomorrow, but since you obviously won't be there I'll give them to you now. He pulled out a bag of what looked to be sweets and I gulped.

"Sweets are for babies." I didn't really mean it, Ukitake always managed to get his hands on the best candy.

"I don't know about that. I myself enjoy sweets every once and a while. Take them, I insist, maybe you can find some other use for them."

Well, when he puts it like that you won't be able to resist. Hyorinmaru sniggered and I absentmindedly told him to shut up.

"Well, I guess if you insist... Thanks, Ukitake."

Told you so...

Oh, shut up!

I left Ukitake's office soon after that, heading up towards the squad four barracks after stopping really quickly at my office- Matsumoto happened to be mysteriously absent- and grabbing a suitcase. I shoved a couple of changes of clothing into it, Ukitake's sweets, the mission report that was sitting on my desk and the stuff I got from squad twelve.

I took my time packing, but then I realised I had stalled long enough. I would have to go to squad four to get one of the emergency first aid kits and while I was there I would have to do something else as well.

I would have to say goodbye to Momo.

I made my way up the hill using shunpo, but my heart wasn't really in it. I didn't want to see Momo, yeah sure, she was like a sister to me, I care a lot about her. That wasn't the problem. The problem was that Momo was unconscious and in a coma because not only had Aizen impaled her, but he had shattered her mind in the process. It was one thing to get stabbed- I've been stabbed myself, I got over it- it was another thing to get stabbed by someone you looked up to and loved while they gave you a hug and told you that they were sorry they had to do this to you. Momo would never be the same, and it was all because I wasn't strong enough to protect her.

Aizen had destroyed Momo, and because of that I was going to force him into a frozen hell for all eternity.

I walked into the squad four barracks and ran right into Unohana. She smiled that so-nice-it's-scary smile of hers and told me she would make up my kit while I went and talked to Momo. The way she said it was enough of an order that I walked to Momo's room as quickly as I could without disturbing the other patients.

As soon as I walked in I felt part of Hyorinmaru leave me. He was going to talk to Tobiume on her inner plane to figure out how Momo was doing mentally.

"Hinamori, I have to go away for a little while." I said, talking to her as if she could hear me. It was the easiest way to deal with this. "I promise I'll return as soon as I can, and if you need to contact me then ask Matsumoto or Ukitake. They can help. I hope you're healing up okay in there, I miss you Hinamori. Everything is going well out here though, hollow activity has been low. I'm sorry I couldn't protect you from Aizen, but I swear I'll never let him lay a hand on you again. I have to go investigate a school of humans with superpowers- can life get any weirder? I swear, they're honest-to-God wizards, with wands and everything. Apparently I have to use a wand too. Man, if you could see me Hinamori you would tease me for all eternity."

I continued babbling uselessly at her until Unohana came into the room, silently gesturing for me to follow her.

I did so and soon we were outside, "How is Hinamori doing?" I asked.

"Her physical injuries will still take a while to heal, but she's well past the danger stage now." Unohana said softly as we walked down the hall, "As for her mental injuries, I suppose only time will tell. I am worried however- Aizen's betrayal hurt her the most."

I nodded and she handed me the supplies, everything from the green knockout fluid to bandages with healing kido attached. "Arigato, Unohana."

She nodded and sent me on my way. As soon as I got out of range of Unohana's hearing Hyorinmaru started talking. I was pretty positive I wasn't supposed to talk with Momo through Tobiume, so we were both careful about what we said around Unohana. Her Zanpakuto had ears too.

Tobiume says Momo is very upset naturally, but she's been doing a little bit better. It'll still take her a long while to stop being destroyed by Aizen's betrayal, and even then it'll still hurt. What Tobiume is worried about is that Momo still has bouts of denial where she still trusts Aizen and feel he must have some reason for what he did. It's these bouts she's most worried about, they're becoming less frequent, but they're still there, and when they hit her she's completely irrational. She's in major denial, Master.

But she's doing better. Are there any long-lasting effects from Aizen's hypnosis?

We can't tell, we can't even tell if he actually used it on her.

Damn that bastard. He has to resort to manipulating little girls to get what he wants, the coward.

Hyorinmaru gave a disgusted snarl of agreement and the two of us quickly returned to the barracks. Rangikou was sitting there, and she was holding something behind her back. "Taicho! I have something for you!"

From behind her back she pulled out a small stuffed white and blue dragon. It was insultingly adorable and I was half tempted to blow it up using kido.

Instead I let my mouth fall open and Hyorinmaru laughed so hard it felt like he was pounding on the inside of my skull.

"Matsumoto... that's a toy."

Oh, I wish I could see the look on your face. Your thoughts are priceless.

She nodded happily, not understanding my concern.

"Matsumoto, I'm too old for toys."

"Oh, I don't mean it that way! I got one for me too!" she held up a stuffed lion, Haineko was not going to be impressed with that, "This is just a souvenir. Something to remember us by while when you're gone."

And when she puts it that way you can't turn it down without being rude! Hahahahaha... you're never going to live this down. The great Hitsugaya-Taicho, youngest to ever reach Bankai and become a captain, with a stuffed toy.

Shut up. You do realise it's meant to represent you, the great ruler of the skies- right?

Hyorinmaru fell silent. Damn, you think I look scarier than that- right? I have to look scarier.

You do, I said soothingly, having gotten my point across I didn't want to hear him whine until he found something else to distract himself with, It's just Rangikou.

"Oh... arigato, Matsumoto." I took it from her and held it by one wing like it was a weapon of mass destruction before walking it over and stuffing it in the bottom of my suitcase. Hopefully no one else would ever see it and I would be able to dispose of it without insulting Matsumoto and listen to her whine about it for a month.

I looked up at the clock and realised that I had five minutes left before I had to get up to the Senkaimon gate. "Matsumoto, I have to go. Talk to Ukitake if you have any problems, or call me if you need to." I grabbed my bag and ran out of the room before she had a chance to respond.

I got up to the gate with a minute left to spare, the head Captain and that Dumbledore man were already there. "Soutaicho," I addressed him, bowing, "Headmaster." I addressed Dumbledore, remembering what Yamamoto had told me he was earlier.

"Are you prepared, Hitsugaya-Taicho?"

I nodded, not saying anything. "Where will I get a gigai?" I asked.

"You will not need one, all wizards can see ghosts." I nodded, happy that I wouldn't have to wear the annoying thing until I realised that unless I found some way to hide him I wouldn't be able to wear Hyorinmaru. And of course, hiding a metre long sword is not the easiest thing to do.

"How will I wear Hyorinmaru then? I cannot defend an entire castle from hollows and murdering wizards without using my Zanpakuto." I said pointedly.

"I believe Dumbledore-sama has a solution for that. Unsheathe your Zanpakuto." I did as he told, nervous about what he was going to do with my partner. Dumbledore muttered something under his breath and all of a sudden Hyorinmaru was nothing more than a charm bracelet in my hand, with the sole charm being a sword. I reminded me greatly of the Quincy's bracelets which contained the bow.

What the hell! Hyorinmaru roared. And the temperature in the area dropped completely low, so low that snow started falling from the sky.

"Yamamoto Soutaicho. I know that this is rude of me, but I would like to know exactly what you have done with Hyorinmaru, and the sooner you tell me, the better." my voice was icy calm, and the sky began to fill with clouds.

Dumbledore spoke for the first time, his voice cheerful, as if he was completely unaware of the danger he was in, "Ah, so you really are a Captain, the reiatsu coming from you confirms it. I had my doubts when Yamamoto said you were a genius, and with enough power to even alter the weather itself. Intriguing, but I guess we should return to the task at hand... If you would please retract some of that pressure you are emitting I will explain what I have done, and if you don't like it we will find another way." I realised I was smothering him, despite how powerful this man was he was obviously still a human soul, incapable of undergoing this kind of strain. His promise of reversing it was enough for us to get ourselves under control and fully undo the damage our spirit energy did so things were back to normal.

"Thank you," he said, "So; imagine that this is just another unreleased version of you Zanpakuto. From what I understand you are able to access three levels of power; bankai, shikai and unreleased?"

I nodded, gesturing for him to continue.

"All you have to do is give you Zanpakuto a command, different from the shikai and bankai commands, and he'll go into his unreleased form. I hear they're picky about commands though, so you might want to talk it through with him."

I nodded, and Hyorinmaru immediately gave me his wish. Command me to arise and rule, master, and I will obey your wishes. Now that I think of it this is actually quite a good idea.

I nodded at Dumbledore, "This is an acceptable idea."

He smiled and said, "Let us be on our way then. I shall explain things fuller once we are in the world of the living, as you call it."

Yamamoto gave a nod of approval. I bowed to him and followed the strange old man through the Senkaimon.