Onotora Shu does not know that his foster father is a legendary professional killer. However, his daily life dramatically changes after someone murders this professional killer. Onotora decides to take over the family business and become a hitman in order to avenge his foster father. He is well prepared when he approaches Narumiya Mitsuki who is his assassination target. Despite his physical abilities as a hitman, he is not able to kill her because of his terrible timing, no matter how he tries....