Koi hi Kogaruru Kamikakushi

Tetsuya Kai sneaks into school after hours to retrieve something he left behind and is suddenly attacked by an unidentified creature called a Shikigami. His classmate Tomomi Soshi appears and drives it off. Tetsuya joins her occult research club — not entirely by choice — and begins pursuing the mystery of the Shikigami that attacked him and, inexplicably, also saved him.