Tomosato Ogino, a brilliant doctor, loses his life in an earthquake while operating on his younger sister. However, he finds himself reincarnated in another world and given the vocation of an "assassin" who specializes in the ability to kill people. As he struggles with the fact that he has lost his sister and his vocation, a girl who looks exactly like his sister appears in front of him...? In this otherworldly fantasy suspense, a former doctor who makes his living as a "revenger" gets involved in various incidents.