Reborn as Eren Yeager: The Gacha System

Eren’s birthday fell on an unremarkable Tuesday, which Carla had apparently decided was an insult that needed correcting.

"We are not," she informed him at breakfast, in the tone of a woman issuing a royal decree, "letting a perfectly good birthday happen on a Tuesday without consequences."

"Consequences meaning what, exactly?"

"Meaning cake. Meaning guests. Meaning you will smile and be gracious about it, because I have already started the batter and there is no taking it back now."

Eren, who had learned several years ago that arguing with Carla once the batter existed was a losing battle on principle, wisely surrendered. "Fine. Cake. Guests. Graciousness. I can manage that."

"You say that now."

By afternoon the house had filled with exactly the sort of chaos Carla had clearly been planning for weeks. Armin arrived first, bearing a wrapped, suspiciously book-shaped package that he insisted, unconvincingly, was "definitely not a book."

"It’s very obviously a book."

"It could be anything book-shaped."

"Name one other book-shaped thing."

"...A very flat box."

"Armin."

"Fine, it’s a book. But it’s a good one."

Mikasa arrived shortly after, and whatever she’d brought, she kept tucked carefully behind her back the entire walk up to the door, which Eren found more suspicious than anything Armin could have attempted.

"You’re hiding something."

"I’m not hiding anything."

"You are extremely obviously hiding something."

"It’s a surprise. Surprises require hiding. That’s the whole premise."

"That’s a very convenient rule you’ve just invented."

"It’s not convenient, it’s logical." She said this with such flat conviction that Eren decided arguing further would only end with him losing, which was, he was coming to realize, the outcome of most arguments with Mikasa.

Disaster, predictably, arrived in the form of Hannes, who showed up an hour later carrying a wrapped gift roughly the size and shape of a large melon and immediately setting off every alarm bell Eren owned.

"Happy birthday, kid." He handed it over with the pride of a man who believed, incorrectly, that this was going well.

"...What is it."

"Open it and find out."

Eren unwrapped it slowly, the way one might approach a suspicious noise in the dark, and discovered — a helmet. A genuine, if slightly dented, Garrison training helmet, several sizes too large, clearly repurposed from actual decommissioned equipment.

"You gave a nine-year-old a helmet."

"A safety helmet. For all your reckless climbing-wall nonsense."

"It doesn’t fit."

"It’ll fit eventually. Growth spurt’s coming."

"This is going to swallow my entire head."

To demonstrate, Eren put it on. It did, in fact, swallow his entire head, sliding down over his eyes with a soft metallic clonk, plunging him into total darkness while everyone in the room dissolved into laughter.

"I can’t see anything," came his muffled voice from somewhere inside the helmet. "Hannes. Hannes, I have gone blind."

"Character building."

"I’m going to walk into a wall."

"Also character building."

He did, in fact, walk into a wall — gently, more of a bump than a collision — which only made Carla laugh so hard she had to sit down, and made Armin laugh so hard he nearly choked on a piece of cake he’d apparently decided the party had officially started regardless of helmet-based blindness.

Only Mikasa’s voice cut through the chaos, dry as ever. "Someone should rescue him before he concusses himself on his own birthday."

"I don’t need rescuing—" Eren said, walking directly into a second wall.

"You need rescuing."

She crossed the room and lifted the helmet off his head herself, revealing his thoroughly disheveled hair and the deeply wounded expression of a boy who had just lost a fight with his own gift.

"Thank you," he muttered.

"You’re welcome. Try not to wear it again until you’re taller than the helmet."

"That could take years."

"Then it’ll be years well spent."

The gifts, once the helmet crisis had passed, turned out considerably better.

Armin’s was, as predicted, a book — battered, well-loved, clearly one of his own favorites rather than something new. "It’s about places past the walls," he explained, a little shy about it. "Ships. Oceans. I thought — I don’t know. I thought you’d like imagining it."

Eren turned the book over in his hands, throat tightening in a way he hadn’t expected. Armin had no idea how close to the truth he’d wandered, handing over a book about the very ocean Eren already knew existed, already knew he’d one day stand in front of.

"I love it," he said, and meant it more than Armin could possibly understand.

Mikasa’s gift, when she finally produced it, turned out to be a small leather pouch, hand-stitched, clearly the product of the same patient hours that had gone into the bird carving and the wristband before it.

"For carrying things," she said, a little awkwardly, which was rare enough for her that Eren paid extra attention. "Small things. Things you don’t want to lose."

Inside, when he opened it, sat a compass — old, slightly scratched, clearly secondhand, but functional.

"Where did you even find this?"

"Traded for it. Took a while." She shrugged like it hadn’t mattered, though the careful stitching on the pouch said otherwise. "I thought — if you’re always looking at the walls, at least you should have something that points somewhere."

He looked up at her, something in his chest going warm and a little unsteady.

"You always know exactly what to give me."

"I pay attention."

"You pay too much attention. It’s mildly alarming."

"You said that about the wristband too."

"It’s still true."

She almost smiled — that small, private one that never quite made it to her mouth but lived entirely in her eyes — and didn’t argue.

The evening wound down slowly, cake reduced to crumbs, Hannes eventually persuaded to remove the helmet from consideration as future birthday attire, Armin curled in a corner already three Chapters into his own gift because apparently giving Eren a book meant also personally supervising whether Eren appreciated it correctly.

Eren slipped away eventually, out to the warehouse, compass in hand, and allowed himself the daily draw once he was sure no one would come looking.

[Daily draw available. Spinning...]

The wheel spun. Slowed. Stopped.

[Result: Titan Physiology — Fragment I (Tier 3, Rare). Basic understanding of Titan regenerative biology unlocked. Full comprehension requires additional fragments.]

Eren went very still.

This wasn’t reflexes. Wasn’t a wristband-sized improvement stacking quietly in the background. This was the first piece of something bigger — the first crack in a door he’d spent a year trying to find, and hadn’t realized the system had been leading him toward the whole time.

"Fragment I. How many fragments total?"

[Query restricted. Additional information available upon further fragment acquisition.]

Of course. Never a straight answer. Just enough to make the shape of something visible, never enough to see it whole.

He turned the compass over in his hand, the one Mikasa had given him hours earlier, needle trembling faintly before settling north.

If you’re always looking at the walls, at least you should have something that points somewhere.

She had no idea how right she was, or how much closer the system had just brought him to understanding exactly what stood beyond them — and exactly what it might cost him to survive what he already knew was coming.

One hundred and fifty-eight days.

For the first time, the countdown didn’t feel like it was just measuring time running out.

It felt like it was measuring how close he was getting.