Grisha Yeager — Eren's father, Mikasa Ackerman's adoptive father, and secretly the current wielder of the Attack Titan. The gift of that power came with a cruel price: a lifespan cut short to just thirteen years.
An Eldian born far beyond Paradis Island, in Marley's internment zone of Liberio, Grisha had come here on a mission — to overthrow Marley's control and free his people. His ultimate goal: seize the Founding Titan, locked away within the royal family inside the walls.
Lock knew this. He knew that no matter how many years Grisha had lived peacefully within these walls — no matter that he'd remarried, had children, and worn the face of a simple doctor — the man had never let go of that purpose.
"One side is family… the other is the freedom of an entire people," Lock thought as he walked away from Eren's home. "Carrying that kind of weight… unable to be honest with even your own family… You must be exhausted, old man."
Karal, Eren's mother, had tried to forbid him from joining the Survey Corps, but she wasn't his real parent, and in the end, she couldn't stop him. Surprisingly, Grisha had voiced his respect for Lock's decision.
Eren had tried to follow his lead, only to be immediately shot down by Karal and Mikasa, a double blow that left him sulking for the rest of the morning.
Lock didn't linger at their door. He broke into a sprint, heading straight for the blacksmith shop. By the time he arrived, his shirt clung to his back with sweat, but the quiet chime of his strange system ability in his mind, [Explosive Power +1], made it worth it.
Over the past days, he'd learned exactly how his "system" worked. Push himself past his limits with a new kind of training, and his abilities would grow. Do the same training again, and it wouldn't count — at least, not until the next day. It meant each improvement was hard-won, but it also meant that in three months, he could push his body to terrifying new heights.
That would be enough to crush the conscription trials.
He also knew the training would get harder as he grew stronger, but that was a problem for later. Right now, there was work to do.
As he approached the smithy, Aunt Martha stepped outside, carrying a plate.
"Lock, you don't need to show up this early. Harry's not even awake yet," she said, holding out the food with a smile. "You haven't had breakfast, right? Try this."
He had eaten already, but one look at her expectant face and he sat down without protest. The meal was simple, hearty, and gone in minutes.
Not long after, Uncle Harry appeared, glanced at the empty plate, and sighed before finishing the scraps himself.
The forge roared to life. Lock hammered metal until sweat rolled down his arms, the orange light of the flames painting him bronze.
Harry leaned on the workbench, watching. He remembered the first day Lock had walked in — just thirteen, small, wiry, asking for work. Harry had been ready to turn him away. Blacksmithing wasn't for kids, especially not ones built like twigs.
But Lock had proved him wrong. The boy's strength matched a grown man's, and his focus never wavered through the endless rhythm of the hammer.
Finally, Harry said, "Boy… want to learn real blacksmithing from me?"
Lock looked up. "Aren't I learning now?"
Harry snorted. "What you're doing now, anyone with strong arms could do. I'm talking about taking it further."
Lock understood immediately — and hesitated. He wasn't here to become a master smith; the forge was just a tool for building his strength for the Survey Corps. He was ready to turn Harry down… until a new chime rang in his mind:
[Achievement Unlocked — "I Am a Little Blacksmith"]