Kobato and Osanai made a pact to lead a quiet life as regular students upon entering high school. However, soon after, a handbag mysteriously disappears at the school, and Kobato is asked to help solve the case.

Kobato finds Osanai crying in the school hallway, but she runs away without telling him what happened. At the student newspaper club, a new mystery involving Berliner Pfannkuchen (jelly doughnuts) awaits him.

Just before a date with Osanai, Kobato runs into Kengo, who shares some disturbing news and leaves a strange message. Together with Osanai, Kobato tries to solve the mystery. However, shortly after, it appears that Osanai is in great danger.

Kobato finally manages to see Osanai in the hospital, revealing a sinister and terrifying truth.