A teenager wakes up on a hillside with no memory except this: he can kill aliens. The world doesn't need him to understand why. It needs him to fight, and the three people learning to live with him need him to stay, and those two things are never the same thing. The animation pulls back and lets silence do the work, trusting you to feel the weight of a boy who exists only because he's useful, learning what it costs to be loved anyway.

An alien invasion pushes humanity to the brink until Arikawa, a member of a small anti-alien task force, finds Kakashi, a teenage boy lying alone on a hill. Tests reveal that this one high schooler holds a power that works against the invaders like nothing else. There's just one problem. Kakashi has no memory of who he is or how to use the power inside him. Arikawa takes Kakashi in to live with himself and his superior, the domineering Shiro, and an odd shared life begins. Caught between Arikawa's easygoing kindness and Shiro's harshness, Kakashi keeps fighting for the family and friends he believes are out there somewhere. A tangled web of feelings forms among the three, and when Kakashi starts to doubt his own reasons for fighting, the fate of the planet hangs in the balance. The OVA mixes action, supernatural fantasy and romance.