It Was I Who Was Mistaken.

間違っていたのは俺だったんだ。

Furuya is thrilled when Sara, a beautiful and popular classmate, confesses to him, but once they start dating her constant surveillance smothers him. Pushed past his limit, he shoves her down a staircase and kills her. Sara had sworn nothing would ever part them, and she keeps that promise, returning as a calm, seemingly normal ghost who simply stays by his side. This dark one-shot turns a yandere romance into a haunting Furuya cannot escape.