Kindergarten teacher Kohei Saeki, who has a past as a professional bounty hunter in America, gradually reverts to his old self after a bomb terrorist he captured during his bounty hunting days escapes.

The escaped terrorist, fueled by his grudge against Saeki, takes his colleague Miyuki Adachi hostage to lure him out.

Moreover, to inflict deeper suffering on Saeki, the terrorist had planted a bomb in the kindergarten.

The bomb is hidden inside the desk of a boy in Saeki's class.

If the boy attempts to escape, the bomb will explode.

To save Miyuki, the boy, and the kindergarten that supports his present life, Saeki attempts to revert to his cold-blooded self from his bounty hunting days.