Rika Akagawa is a classmate of Kenta Kogure, lured with him and others to an abandoned school building by mysterious letters. She harbors a secret romantic interest in Kenta, who remains oblivious. Petite with a notably youthful appearance often mistaken for that of an elementary schoolgirl, Rika wears large glasses fitting the "Meganekko" archetype and exhibits a reserved personality.

Once trapped within the building, Rika becomes the first to vanish. Her abduction is followed by the appearance of a video depicting her violation by an assailant, escalating terror among the remaining captives. This event marks a pivotal moment, underscoring the immediate threat posed by their unseen captor.