Summary: A new spell let Lucy enter into Natsu's mind. As she wandered through his memories, she learns about Igneel through Natsu's eyes and discovers a shocking secret about his family. Spoiler hints for chapter 436.

A/N: This is my entry for NaLu Week 2015's Wander prompt. I decided not to make a compilation fic this year 'coz I feel this piece deserves to be its own fic.

Disclaimer: Fairy Tail and its characters belong to Hiro Mashima. I can only claim the spell Lux Mentis, that's all.

Lucy bit her lip and inhaled deeply as she tried to calm her nerves. Meanwhile, Natsu has positioned himself in front of her on the couch, eyes closed and looking totally relaxed.

"A-are you really sure about this Natsu?" she asked again. "Is it really fine to do it with you?"

Natsu opened one eye and peeked at her. "Yep. Totally fine."

"I mean, it's my first time doing this." She averted her eyes from him and started fiddling her fingers. "I-I might hurt you if I do it wrong."

"Hey," he said softly, both eyes now open. "If it's you, I'm sure that won't happen."

She looked back at him again, her eyes filled with worry. "But-"

"No buts, Lucy." He met her eyes and leaned forward, touching his forehead with hers. "I believe in you. You'll do fine. How will you learn if you don't try it?"

"If I didn't know better, I would think you're doing some nasties in there guys." Happy commented from the chair across the room.

Lucy's head whipped towards Happy, an embarrassed flush on her cheeks. "We're not!"

"Do we now, huh buddy?" asked Natsu who was slightly blushing as well.

"Aye." Happy nodded. "You liiiike each other, do ya?"

"Happy!" Lucy shouted.

Natsu chuckled at Lucy's outburst that quickly turned into a laughing fit.

"Natsu!"

A quick slap to his thigh and a matching pout got him laughing even harder.

"It's not funny!" She fisted her hands and was about to pound on Natsu's chest when he caught them.

"There, that's the Lucy I know!" He was grinning at her. "It isn't really like you to hesitate."

She looked up at him and just sighed. "Yeah, you're right." She straightened up and settled back on her place. "Sorry 'bout that. It's just, the spell will really intrude on your privacy, so it kinda feels wrong."

"Lucy, we talked about this already right? This spell, Lax me-mental?"

"Lux Mentis." she corrected. A spell she read on a book Celestial Magic she got from Levy. The book included a chapter about keyless spells for Celestial Mages which mentioned a lot of notable spells including Urano Metria, Gottfried and the spell they are currently trying to do, Lux Mentis.

"It lets a celestial mage unlock a target's memories by exploring them. In this case, I'll be unlocking your mind and I'll be able to see your memories from childhood up until now." she explained again.

"That's what you said." Natsu nodded.

"Hey, I might see something I can blackmail you with. Are you good with that?"

"I know you won't do that. I trust you."

"Natsu." She really can't believe that he trusts her this much. "I can't screw this up when he's so confident of me." Lucy thought to herself.

"Besides, I wanna remember more about my childhood. I can't seem to remember things before meeting Igneel. You can unlock those parts, right?"

"I think so." She nodded again.

That was what makes her anxious about this: Igneel. She knows how important Igneel was to Natsu. Even before the events of the war against Tartarus, her friend loved his dragon father so much. She will be seeing those times he spent with him and so much more.

"I really wanted you to meet him, Lucy." He said softly. "I wanted him to meet you and Happy."

"Natsu." was all she can say.

"We were occupied when we last saw him, weren't we?" A wistful smile settled on his lips. "He would have liked you and Happy a lot."

Lucy squeezed Natsu's hand which was curled up on his knee. "I'm sure we would have liked him too, Natsu."

"Yeah." Natsu nodded, his smile brightening. "So tell us what you think of him after this alright? It sucks that Happy can't join you but he'll settle with your story, right buddy?"

"Aye! Tell me lots about Natsu's memories after."

"Of course." she smiled at them both.

This spell was not just a new addition to her arsenal. It's a spell that will let her connect with Natsu's past. It's such a big honor as his friend so she has to do this right.

"Let's do this." She looked at Natsu one last time and he met her eyes with encouragement.

She slowly closed her eyes, letting magic power flow through her. The spell requires the caster to treat herself as a celestial key and the target's mind as a gate.

"I am the guide, the beacon
of the lone star in the vast heavens.
Oh Ego, be free and reveal your light.
Shine, Lux Mentis!"

She felt a strong pull coming from Natsu and she let herself go. Soon, the force brought her before an intricate gate in various shades of red and black. And in her hand, a simple golden key that she slipped into the keyhole. She turned the knob and entered what she believed was Natsu's mind.

She didn't know what she expected but whatever it was, it's not what's in front of her right now.

Rows upon rows of doors in different stages of aging. Some doors, the ones near the gate were relatively new. The paint on them still looked fresh and the knobs were still sparkling. Meanwhile, the doors which were quite far from where she stood looked worn and old. Some doorposts even had cobwebs on them.

"Now, the book said the number of doors inside a person's mind would approximate his age." she thought out loud. "But how are there so many? Natsu doesn't remember his exact age, but he's not that old, is he?"

"Well, whatever." She shrugged and started walking. It's not an issue at the moment. Confirming if she did succeed in the spell comes first.

She tried the first door. Unlocked. It swung easily and Lucy entered slowly. "Hello?" She called out tentatively. Inside the room, she could see herself in a projection. "This must be his most recent memory. That's me in my living room when we started the spell."

She deemed that as confirmation. They did the spell right. She exited the room and started for the next door. "This shouldn't be that long, I hope. Maybe just a few weeks or months ago."

Again, the door was unlocked although it didn't swing as easily as the first one.

It was from the time they stopped Avatar from doing the Purification Ritual.

"Comrades are the people that share the same purpose and move forward with you! Their purpose doesn't even have to be the same as yours!" Natsu shouted. "They'll laugh with you, be by your side when you need them… You believe and trust each other."

"Dependence, that's what it is." said Arlock.

"It doesn't matter what you call it... That bond was all I needed to keep me afloat! So don't you make light of our bonds!"

Her own mind flooded with memories of her own from that time. It was an awkward time for her back then. Natsu and Happy came back into her life like a raging storm and swept her off her feet. They traveled together just like the old times but a nagging question bothered her every night. Why did they leave her behind? She wanted to ask him directly but Natsu has his own way of answering her unspoken questions.

He left so could get stronger. He left so won't lose anyone again. And in his time of grief, it was the memory of his friends that kept him afloat.

It's funny how similar they are sometimes.

Lucy left the room with a pensive smile on her lips. Looking at Natsu's memories sent her on a trip down her own memory lane as well. It's natural since they spend a lot of times together.

She skipped on a few doors until she arrived on a gloomy looking one. It still looked new, but it was quite different from the other doors before it. There was a latch lock right above the knob. It gave her the impression that Natsu tried to lock away the memory behind the door but can't. The knob was unlocked and the latch lock didn't really serve its purpose as it was placed outside.

She has an idea what the memory could be.

With shaking hands, she turned the knob and entered.

"IGNEEL!" Natsu's voice shouted.

Lucy gasped at the sight and stepped back. Tears filled her eyes as she helplessly watched the horrible sight.

Igneel was spiraling fast to the ground with a large chunk of flesh missing from his side.

"Oh Natsu." She cried. She knew about this. He told her days after the fight and before he left with Happy.

She thought she understood him. She already lost her parents so she thought she understood his loss. She was wrong.

"Stupid, stupid." She berated herself as she sobbed. "Stupid." A minute after, she quietly left the room.

She still felt heavy and sad as she continued to explore. At one point, she wanted to stop but she remembered Natsu's request. He asked her to look for the memories of his childhood. The ones he spent with Igneel so she can share it with Happy. He also wanted her to find the memories before he met Igneel.

The doors progressively got older as she walked on the corridor. It got darker as well. Perhaps they reflected how Natsu remembered them. The less he remembers about it, the older they looked. Cobwebs started to show up to, some of which clung on her.

She decided to peek into one again, knowing that she's still a little far from her real target. The door was frayed and the knob had a lot of rust. When she turned it, she had to use a little force to get it to open. The memory inside was a little blurred and the sounds

"Erza!" Young Natsu called out. "I challenge you! This is the day I will beat you."

"Very well." Young Erza drew her sword and took a stance. "Come, Natsu!"

"Fire Dragon's Iron Fist!"

Lucy almost got dizzy when the view turned and wobbled. Erza finished off Natsu in an instant.

Lucy felt a little bad for Natsu. He was very determined to win. She knew by their friends' stories that her dragon slayer friend kept challenging Erza non-stop until she came to Fairy Tail. Come to think of it, he's not challenging Erza anymore recently.

"Guess Natsu matures too, even slowly." She giggled at the thought.

She got out again and went further down the darkening corridor. She has passed at least 15 doors now, but why are there still so many doors? She could see at least 20 more doors.

"Is this what you would call an 'old soul'?" Lucy wondered. "Or does Natsu actually remember a lot, just not vividly?"

A strange door got her attention. It was the only door in the area in still good condition unlike its neighbors which were frayed and old. "This might be it. He said he still remembers his time with Igneel clearly."

Suddenly, her heart beat faster and her hand was clammy. "Come on Lucy, no need to be nervous. You won't talk to him. You'll just see him through Natsu's eyes. It's not like you're meeting your father-in-law, right? Right."

But she really was nervous. She'll be seeing a precious memory of Natsu's if her hunch is correct. She still has her reservations about intruding on Natsu's privacy despite having seen his other memories. This one memory is different.

She inhaled deeply and psyched herself. "Natsu allowed me to do this. It's alright." She reached out and touched the smooth knob. It surprised her when the door already swung open even before she turned it. It's as if Natsu was welcoming her himself into the room.

The room was warm and cozy, just like how a loving home would feel like. It reminded her of the time when her mom was still alive and her dad was still affectionate with her. The room was full of parental love.

"Natsu, come here."

Lucy immediately recognized the red dragon before her. Igneel.

Little Natsu came running and hugged the dragon's snout. "Dad, look at this!" He opened his hand. A small flame danced on his palm. "It's warm, just like you."

Lucy smiled at Natsu's remark. He was so innocent.

"Of course." Igneel chuckled. "We're fire dragons.

"When I'm as big as you Dad, I'm gonna make the biggest fire ever!"

"Then grow up big and strong, my little dragon slayer." Igneel nuzzled Natsu's tummy, earning giggles from the little boy.

"He's wonderful, Natsu." Lucy wiped the tears falling on her cheeks and sniffed. "It would have been amazing to meet him."

She stayed longer and watched as more memories played before her. She saw when Natsu made his first dragon roar, when they flew the skies to hunt for food and lots more other moments that Natsu spent with Igneel.

It broke her heart when the final memory played. July 7, X777. Natsu woke up that morning, his dragon father already gone. No matter how hard he called for him, Igneel didn't come back for Natsu.

Lucy was a tearful mess when she finally exited the door. "You truly loved your father so much, Natsu. Thank you for sharing that memory with me."

She wiped the remaining tears on her face and tried to make herself decent. It was disorienting to be back in the dark corridor after staying in very cozy room. The chill earlier turned freezing and somehow the place got creepy. It's hard to believe that she's still inside Natsu's mind, someone she knew as a very cheerful and warm person, when it's this cold.

It's like she's in a completely different person's mind.

She continued to walk past the doors of which she believed held Natsu's memories prior to meeting Igneel. Will these doors show her his biological family? How did his human parents look like? Did he have siblings? Brothers or sisters?

The doors all looked menacing. The wooden doors were replaced with rusted steel ones. Nothing looked inviting at all. In fact, everything seems to say "KEEP OUT" and Lucy shivered at this thought.

"I have to try. I promised Natsu to unlock these."

She looked for the least scary door and tried to summon her magic. Unlike the wooden doors which had doorknobs, these steel doors only had deadbolts on them. So she needed to conjure up a key to open them. She concentrated hard and after a few seconds, a simple steel key was on her hand.

She inserted it and turned. As expected, it didn't turn easily. Using two hands, Lucy turned the key until it finally gave way. The door creaked loudly as its hinges were heavily rusted as well.

It was dark inside the memory room. She could only see silhouette accompanied by soft voices. Even so, she could tell that the memory was chaotic. People (she thought those were silhouettes of humans) were running away from Natsu. She could make out some screaming. Which was confusing since he's supposed to be a young boy at this memory right? He wasn't older than seven years old in those memories with Igneel.

Why would people run away from a kid?

The dark movie continued on. Lucy wanted to get out already, feeling scared and confused. But then, the memory lighted up. It was still blurred but she could hear the words more clearly now.

"Nii-chan!" said Natsu in a very baby-like tone.

"Natsu." a voice called back. "Ah, careful!" The person bent down to pick up Natsu. "Are you hurt?"

Natsu just giggled and reached for him. "Nii-chan!"

"You're quite spoiled, aren't ya?" Natsu's brother chuckled.

"Natsu has a brother! Does he know about this?" Lucy's mind was running a mile a minute. "He still has a family. I have to tell him!" Suddenly, Lucy felt weak. Her hands started to shake and the memory was becoming dark again. The voices were turning into whispers. "What's happening? Am I out of magic?"

"Nii-chan."

"Natsu, my brother." There was fondness in the voice that clearly showed that he cared a lot about baby Natsu.

"No, no, I have to see this through. I haven't seen his brother's face properly!"

"WAIT!" Lucy shouted. She was breathing heavily and her surroundings had changed. She was back in front of Natsu inside her living room. "Natsu." She gasped.

Natsu slowly opened his eyes too and smiled at her. "Hey."

"H-hi." She stuttered, still overwhelmed from her recent spell. She felt drained and wobbly. Natsu quickly caught her before she fell face-first on her couch.

"You alright?" he asked her, his breathing uneven as well. Lucy wondered if the spell affected Natsu's magical reserves too.

"Yeah, I'm fine." she straightened up but Natsu didn't let her go yet.

"Welcome back!" Happy greeted. He crossed the room and settled beside Natsu. "Did you see Igneel, Lucy?"

Lucy nodded at her friend. "I did." She looked up to Natsu and smiled fondly. "He was wonderful."

Natsu returned her smile with a grin. "I know."

After knowing how hard it was for him to accept his father's death, Lucy felt very relieved to see that he could already smile again when talking about it. It really doesn't suit Natsu to be sad and miserable.

"I also saw something new." Lucy continued. "Natsu, did you know you have a brother?"

"I have a what?" Natsu asked, not quite believing what he just heard.

"A brother." She tried to recall what she saw before she was pulled back to reality. "In one of your earliest memories, during the time you haven't met Igneel yet, you were with your brother. You kept calling him 'Onii-chan'."

"Natsu has a brother?" Happy repeated.

"You really can't remember?" Lucy asked Natsu. "Lux Mentis is supposed to unlock memories. Did I fail?"

"He called me spoiled, right?" Natsu asked back. "I-I think I can remember a little but it's all so blurry. It's just his voice."

"Yes! That's him, Natsu!" Lucy felt happy. Her spell worked. "Do you know what this means, Natsu?"

"Natsu still has a family out there!" It was Happy who answered. "A family aside from Fairy Tail."

"I have a brother." Natsu mumbled. "Happy, Lucy, I have a brother!" He gathered them both and embraced them. "Guys, thank you. Lucy, thank you for this."

Lucy smiled fondly at him. "You're welcome."

"We have to find him Natsu!" Happy suggested. "He must be looking for you too."

"Yeah, we'll find him buddy. You'll help us, right Lucy?"

The excitement in his eyes touched her heart. She never thought she would see him this happy again. Just knowing that he still has a family out there brought back the light in his eyes. She wanted to keep it this way. She wanted to protect that happiness. So her small smile turned into a confident smirk.

"Thought you'll never ask."

...

...

A/N2: if you're screaming right now, please consider doing it on review. XD