Kujira is the strongest assassin who controls the killing scene in Japan. His existence has been the common sense and deterrent for the industry, and to a certain extent, the order of the underworld has been maintained. The story begins with Kujira's death. Some take advantage of Kujira's death, some aim to take his place, and some sip the sweet nectar from his corpse. As a battle breaks out over Kujira's chair, a single assassin appears in front of Kitagami Kuroo, a timid young man who lives an ordinary life without knowing the common sense of the underworld... After learning of the conflict over Kujira, the young man steps into the sea of ​​carnage.