A story about a man named "B".

Etsuko Morohashi was a prisoner who claimed innocence but was sentenced to death. The sentence was seemingly executed, but she survived. Then, she was told by a mysterious man that he will change her identity and keep her alive as a different person if she agrees to become an assassin. If she refuses, she will die, but if she agrees, she will see her son after five years. Etsuko becomes an assassin for a mysterious organization as "Saeko Kirihara" so that she can someday be reunited with her son.