The story of [Y/n Aaltonen], the Grandson of [Angel Aaltonen] the creator of 3D gear. But, we're not talking about a regular human here... Have you heard about Monster? Beast?
Kaiju?
Yn was an orphan who lived in a orphanage. One day, Yn was beaten by a group of kid in town, that was until [Levi], the [The Strongest Soldier] safed him and then take him home. Year have passed, Yn grew with Levi as a brothers. The existence of Yn is almost like a secret, no one ever know he lived with Levi, except for Levi's team.
Yn rarely get out and mostly spending his time in his workshop, making weapon. Since his grandfather, [Angel Aaltonen] is the [King Of Inventor] and the one who created the 3D maneuver gear. Beside of him being a weapon genius, Yn is a well trained soldier, thank's to Levi.