After an assassination attempt on him, Koori Takami is called in to help the person who tried to kill him, Kasumi Yukihara, a skilled assassin full of secrets. As he learns more about her, he becomes embroiled in a plot of mystery and tension, meeting Miyu, a girl who falls in love with him at first sight. While Koori deals with the conflicting feelings that arise, Kasumi, determined to prove her strength, finds herself unable to cope with compliments and kindness, becoming an enemy difficult to understand. Between danger, romance and the unexpected, Koori will have to choose between helping the assassin or distancing himself from her, all while dealing with Miyu's growing affection and the complex emotions that the two girls arouse in him.