The Night Beyond the Tricornered Window

Kosuke Mikado, a bookstore clerk, is able to see ghosts since he was young, which terrifies him. One day, he meets Rihito Hiyakawa, a fearless exorcist who lacks social boundaries. Hiyakawa is able to see and exorcise ghosts by entering Mikado's body and requests him to become his assistant. As the two work closely together, they learn that the supernatural incidents are closely tied with a high school student named Erika Hiura, who works as a mercenary necromancer to cast curses on other people. As Mikado and Hiyakawa investigate, Mikado begins realizing that Hiyakawa is hiding a secret.