Rônin Akitsu Masanosuke is a skilled swordsman, but his personality often causes him to be let go from his job. One day he encounters Yaichi, the leader of a group calling itself "Five Leaves" and takes a job from him as a bodyguard. Though he is worried about their intentions, he feels there is something more to the group and agrees to work with them.

Mochizuki General Hospital boasts some of the most well-trained nurses in town. But though these ladies spend much of their day battling sickness, their after-hours are spent fighting a very different sort of disease... Under the leadership of the hospital chairman, a handful of staff members and local teenagers form a group of mercenary assassins, targeting the "cancers" of society and excising those individuals before their wickedness spreads.