Over coffee, Eru opens up to Oreki to explain why she joined the club, and asks him for his help with a personal matter. Still unable to locate any anthologies, the club members run into an obstacle when trying to search the club's previous room.

Hotaro's history class is interrupted by an outburst coming from Eru's math class, prompting a discussion in the Classic Lit Club about the nature of the seven deadly sins, and what might provoke Eru to become angry.

After meeting with Irisu, Hotaro has a change of heart, and sets his mind to solving the murder mystery. Hotaro and Satoshi discuss the nature of their own potential, and what each of them might be able to accomplish.

Hotaro's sister returns home, and sets her lethargic brother up with a temporary job filling in as a lifeguard at the city pool. Satoshi invites Eru and Mayaka out to see Hotaro at work, and the group stumble upon a minor mystery to be solved.

Satoshi is ready for Jumoji to strike, but when the anticipated target is passed over, he must reconsider his strategy. Tomoe gives Hotaro a copy of "A Corpse By Evening," and Eru notices that the art style is similar to one she has seen elsewhere.

Hotaro tells Eru that he can come up with a plausible explanation for any situation she can think of, so when a seemingly mundane schoolwide announcement is made, she challenges him to figure out the reason behind the announcement.