College student Hachi is fed up with his life and seeking a change, leading him and his best friend Tanuki to perform a strange ritual they discover online. The next day, the mysterious "Izzy" arrives in his life.

After Hachi stumbles upon Izzy's first murder scene, he and Tanuki hatch a plan to banish her from the mortal plane. Meanwhile, Hachi's father, Detective Inukai, is assigned the murder case.

Izzy is injured in a fight with her old, undead nemesis. Hachi must figure out how to save her. But to do so, he needs to know the truth of Izzy's mission. Detective Inukai's investigation deepens.

Izzy's hunt for her next target takes her to Hachi's university and his circle of friends. Detective Inukai's investigation leads him to a shadowy group of corporate leaders.

While Hachi and Izzy search for a way to continue her mission without killing, Detective Inukai and Sargeant Suzuki discover the corpse of a missing student. Things come to a head at Detective Inukai's surprise birthday party.

An enraged Izzy attacks her next target while Hachi desperately tries to stop her from killing again. Detective Inukai finds his son is involved.

With Izzy missing, Hachi is confronted by his father about his involvement in the killings. Meanwhile, Hachi's friends are attacked by Izzy's enemies, who are searching for her.

Izzy's friends and enemies collide in a final battle, but only Hachi can change the course of their bond.