It's the last day of summer vacation and Koyomi looks for Mayoi to return the backpack she left behind at his house. On the way, he has an encounter with Yotsugi who reveals that just like him and Mayoi, she once died, but while Koyomi was transformed into an immortal being and Mayoi became a ghost, she was revived by Yuzuru as a shikigami to serve under her. With no sign of Mayoi, and with Yotsugi's words on his mind, Koyomi returns home and keeps thinking about what he could do for Mayoi until he is reminded by Shinobu that he has only a few hours to finish his summer homework...