Let's get right into the action. To recap, so far the casualties are as follows: Ryunosuke, Caster, and like 20% of Assassin. Not bad for the first night of the war. I wonder what else Saber can get done while his dad spends some time with Iri before falling asleep in peaceful ignorance.

3rd person POV, amusement park, minutes after the massacre.

'Iri's having the time of her life, who would have thought that some of her best moments would happen during a cursed war. Maybe we should bring Illya next time…' Kiritsugu thought, a small smile on his face as he stared at his wife having the time of her life on the merry go round. That was until he felt a familiar presence next to him, his smile faded, keeping his face professional as he addressed his servant.

'Sorry to disturb you, master. I'm reporting in and I have a small request.' Kiritsugu heard through his telepathic link, steel, and a hint of sheepishness making their impressions on his mind.

'Very well, go ahead.' The assassin thought, slightly annoyed at being interrupted, though he wondered what a servant wanted from a regular human.

'Caster and his master are dead. As well as a few Assassin bodies, I also gave our enemies a message so we should be safe for now while they keep their cards close to the chest.' That was...Ok, wow. Kiritsugu knew that his servant was strong and had an advanced warning on each enemy servant but this was impressive nonetheless.

'As for my request...I need to borrow some money. About 50,000 yen should be more than enough.'His servant...Was asking him for a loan? Why? What does a servant need money for? 'I need a disguise to pull off my next plan, as well as a fake permit in order to infiltrate a certain place. And...I'd rather not steal if I could help it.'

"...What the hell, use it wisely." Kiritsugu said out loud, going along with the madness. His servant already more than pulled his weight. If forking over a few thousand yen meant more quality work then he was happy to pay up. He also didn't want to know how and why his servant had knowledge of the city's local underworld in order to get said fake permits.

1 Hour later, Matou mansion. Saber POV

'It's time, I should have done this sooner but...Caster was too much of a threat, and from what I learned Sakura's 'training' began long before I was ever summoned. I can only hope that she can forgive me for making her wait a few more hours.' I thought as I walked up to the Matou mansion, dressed in an old favorite of his. A janitor's outfit.

Checking myself over I made absolutely sure that I kept my magic to myself, forcefully closing my circuits for extra stealth. In addition, I had a dagger styled copy of Gae Dearg strapped to my back. Serving its purpose in a roundabout way by preventing any of my mana from escaping from my body. Seeing that everything was in order I knocked on the door.

A few seconds later someone opened the door. A person that gave me the sharp, nearly overpowering urge to punch them in the face. Then I realized that Shinji was still probably a child at this point so it couldn't possibly be him...Then I realized that this was probably Shinji's father who he likely adopted some of his personality from, which reignited my anger once again.

"Who are you, and what business do you have here?" He asked with suspicion. His eyes shifty and narrowed.

"Hello, my name is Fujimura Shirou. I'm here on orders from the city council to investigate some complaints from the locals. Apparently, they've been smelling strange scents coming from your home and some even spotted some strange insects around the property." I explained before handing the Matou my false permit, provided by the local Fujimura yakuza branch. Normally this would harm his foster family, but thankfully he wasn't planning to leave anyone who would target them alive anyway.

"...Very well, you may look around but stay out of the basement and attic. Those are private and we'd like to keep it that way." He emphasized the basement, aka the worm pit. "Normally you'd need to speak to grandfather about this but he's...Out for some business of his own." In other words, he was probably eating some poor schmuck to add a few weeks to his lifespan like the leach he was.

"That will be more than enough, feel free to follow me if you must, I only need to look over the property for a few minutes. By the by, are there any more people inside this building at the moment?" I needed to find out where Sakura was asap. Knowing that Zouken wasn't here was a godsend but if I could grab Sakura before anything else then this would go much more smoothly.

"...There are two, my son and daughter. I suppose if you are going to be spraying poison around I should keep those two gremlins on a fairly short leash." A poor choice of words. I was debating on whether I should leave this human-shaped stain alive but his attitude towards his own children, even if Sakura was recently adopted, disgusts me.

Waiting several seconds while Byakuya grabbed the kids I got my first look at young Sakura. Her eyes were dead, she didn't even frown her face was just completely blank. As if she wasn't even conscious and just went through the motions… I was going to enjoy this far more than I should.

Moving across the building I placed hidden magical catalysts, each connected to its brothers via their identical signatures. Keeping them hidden from Byakuya was surprisingly easy given his ineptitude as a magus(not that I could really judge) but surprisingly Sakura was able to notice, thankfully she kept silent but was now looking at me with barely contained fear. After all, for her, magic meant pain.

I didn't want to push my luck and risk Zouken coming back so once the last catalyst was set I acted immediately. I sped behind Shinji and chopped him in the back of the head, knocking him out before he even realized I moved. Byakuya came next, this time I was much less merciful. A nameless, mundane blade took off his head with minimal resistance.

Finally, I use Structural Grasp to find the main crest worm within Sakura. Seeing it right above her heart I create a copy of Rule Breaker, plunging it in just enough to destroy the worm without killing her.

"*Gasp!" That was all she said, her body didn't move and her expression barely changed even with a blade in her chest.

"Even with a blade in your heart, you do not cry out. What have they done to you little one? I suppose it doesn't matter now, I've freed you from your magical leash. And if you wish, I plan on destroying this place and leaving nothing behind. Would you like to watch?" I asked the young girl, not revealing that I knew her from before. For the briefest moment light returned to her eyes and a small smile came to her face.

"Mister, just what are you? Are you a mage too?" Sakura asked me while starring at the several pillars of pure magical energy that rose where her hell used to be.

"Not quite, if you could compare me to something it would be a ghost. I'm technically dead." I try to explain in simple terms and immediately regretted it when Sakura's smile fell and her mood dropped considerably.

"So you can't be my big brother?" My heart broke at those words. Damn it Emiya, fix this!

"W-wait, I might not be able to stick around but I know some very nice people who can fill that role! My master wants nothing more than to be a hero and his wife would absolutely love you. Plus you'll have an older sister too!" Though with their personalities she'd act like a younger sister most of the time.

Her smile came back, albeit smaller than it was before she knew that her savior was a literal deadman. "And there is a small chance that I could be sticking around for far longer than I think." I admit, not wanting to give her false hope but opening her mind to the possibility at least.

"...I'd like that. What about grandfather? He's still out there isn't he?" She asked with fear in her eyes, though it was considerably less than it used to be since she had the equivalent of a superman sitting next to her.

"He is. But he won't be for long. Most of his worms are dead and the old leach is probably catatonic at this point, if not I'll find him. Either way, he is no threat to you anymore, I promise." She would not be harmed, never again.

"Let's go, as satisfying as this must be to watch we need to leave before Shinji here wakes up." As crass as it was to say, Shinji was a loose end. His family was dead and he had nowhere else to go. This Shinji was relatively sinless, his ego was still under control and he had little to no hatred towards Sakura.

'I suppose it's not the worst thing, maybe he'll even be understanding of the truth if we are gentle about it.' He was never very good with emotional trauma. One of his many weaknesses as a hero. 'I wonder if Kiritsugu would mind another so- a son and dau- three children. The Emiya family is fucking complicated.'

Alternatively, I could leave Shinji at the Tohsa- Oh wait, Tokiomi died too and that left Kirei… 'Do I really want to save a man that would sell away his daughter out of convenience? *Sigh, curse my Origin.' And her mother was equally guilty, being complicit with the whole thing. I guess that means I need to meet Kariya next, but one thing at a time.

The next day, early morning, Einzbern Castle. Kiritsugu POV

If someone asked me whether I would ever wake up sleeping next to a beautiful, extroverted goddess of a woman after a night of wholesome fun, during a mission, he'd laugh straight in their face and asked them what they were smoking. Now. I was just enjoying the peace and quiet.

'Master we need to talk.' "Root damn it, couldn't he have waited five more minutes?" I stand up with the deepest of winces and get dressed before walking off into the main hall where I could sense my servant.

Reaching the large room I was met with a peculiar sight. "Saber, why are there two sleeping children on our couch." I asked the obvious question while staring at the blue and purple tufts of hair that were peaking out of a blanket.

"They are Matou Sakura and Matou Shinji. Byakuya is dead, their worm pit has been destroyed, and Zouken will finally rot away in due time. They just need a place to stay and I thought Illya could use some friends, maybe even siblings?" ...This servant was going to be the death of me.

Hours later 3rd person POV

Shinji was still throwing up in the bathroom, maybe Saber should have censored a bit of the stuff Zouken did. Most adults would probably be dropping their breakfast from that horror show, let alone a child. At least he had Sakura around to comfort him. And to Kiritsugu's surprise, the two kids actually got along rather well with Irisviel.

"Aww, aren't you just adorable! And how do you have blue hair? Or purple? I have white hair but that's because I'm a homunculus." Were Irisviel's first words to the two kids when she saw them walking around. And to make it even funnier the two kids actually stopped to think on it for a minute. With Sakura it made sense, magic was used to change her very DNA and a few side-effects were to be expected. But Shinji? That blue hair was natural...Somehow.

'Then again I'm a pure red-head in Japan. With amber eyes of all things.' Saber thought, still confused about that. Maybe he had a foreigner for a biological parent? And his own magic circuits were also strange, 27 circuits, albeit very poor ones. Not exactly common for a first-generation mage.

Existential crisis aside there was business to be done. Never before did Saber appreciate the fact that servants didn't need to sleep more than now. "This is nice and all master, but I really should get back to work. If I'm lucky we may have a new ally by the end of the night." 'Wait did I just say what I think I just said.' Saber thought with a look of horror on his face.

Minutes later, Saber POV

Once again I dodged for my life, only barely avoiding the "super sonic golden missile of death™" as dozens more came raining down. "You ruined my entertainment mongrel! Now all that dog's master does is manically switch between crying and cheering over the fate of that little purple mongrel!" Translation: Kariya had a mental breakdown and Gilgamesh got bored of it very quickly. Now he's taking his boredom out on me.

'Note to self, never say the L word in a sentence ever again.'

A wise decision young protagonist. A wise decision indeed. Welp, that chapter took longer than I thought it would. BTW I'm just gonna explain it here since I can already sense the question being asked several times over.

That thing that Emiya did with the magical catalysts is basically the same as what he did against Assassin(Shinji) in Oath Under Snow but on a much wider scale. Basically he used a combination of Kanshou and Bakuya's anti-monster properties(for the worms) and the anti-army properties of Caladbolg(for a large AOE) and broke them to create a concentrated area of destructive force.