A high school boy Hotaro Oreki has no energy, and always wants to be efficient in his life. His sister Tomoe offered him to join the classic lit club that faced the prospect of disbandment due to no members. When he goes to the club room, there is another charming applicant for joining the club.

Eru grows bored of the club's lack of activities, and suggests that they prepare an anthology to submit for the school's culture festival in the fall. While tracking down previous anthologies, the club discovers a mystery in the school's library.

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.

Eru decides to solicit Satoshi and Mayaka's help hypothesizing what happened to her uncle. The club members meet at the Chitanda estate, where they present their research and surmise what they believe happened 45 years ago.

Hotaro is torn between continuing with his gray life and the rosy life that the others live. A phone call from Hotaro's sister leads him to believe that there are pieces missing to his theory regarding the events of Sekitani's expulsion.

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.

During summer vacation, the Classic Lit Club members take a trip into the mountains to stay at a hot springs resort inn run by Mayaka's relatives. While there, Eru and Mayaka see what appears to be the ghost of a man who hanged himself!

One of Eru's acquaintances invites the Classic Lit Club to a screening of a student film made by the members of Class 2-F so they can offer their opinions. When the movie takes an unexpected turn, the club is called on to help find a solution.

In search of a conclusion to their movie, the assistant director, the prop master, and the publicist meet with the Classic Lit Club members one at a time to propose their solutions to the unfinished murder mystery.

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.

Mayaka, Satoshi and Eru criticize Hotaro for ignoring Hongo's feelings. Why didn't Irie ask Hongo for the story through Eba? --- He just realizes what Irisu really wanted him to do.

It is the first day of the school culture festival, and the club members look forward to it with both longing and dread. They must come up with a way to sell all of the copies of Hyouka that were printed, as dauntless as the task seems.

Satoshi tries to use the Quiz Club's quiz show event to promote the Classic Lit Club. Eru goes around beating the bushes for ways to help sell all of the copies of Hyouka. More and more items end up missing from various clubs.

The Classic Lit Club cooking team competes against three other teams in the Cooking Club's timed Wild Fire competition. However, Mayaka is delayed drawing posters for the Manga Club. Will she be able to finish in time to compete?

When the members of the Classic Lit Club talk about the happenings in the festival, they find the theft cases are occurred by Jumonji consecutively. From the signature on the cards that the thief left, Hotaro infers that Jumonji has the other meaning, not a last name.

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.

The members of the Classic Lit Club get a lot of students in the club room to catch the thief. The club magazine Hyouka No.46 sells like wildfire because of that.

A helicopter in the sky reminds Hotaro of the teacher Ogi of his junior high school days. Hotaro has assumed that Ogi likes helicopters because Hotaro saw that Ogi had a relieved smile when Ogi found a helicopter through a window during a class. But, Satoshi tells him Ogi wasn't interested in it. Hotaro is curious about why he smiled at that time.

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.

At New Year's, Eru invites Hotaro to join her in paying her family's respects at the town shrine. When Eru agrees to run a quick errand, however, she and Hotaro find themselves in an unexpected and compromising situation.

Japanese people have a custom that girls confess their own love to the boys with a chocolate on Valentine's Day. Mayaka has prepared a chocolate for Satoshi with the help of Eru, but it was stolen from the club room on the day.

Hotaro is enlisted by Eru to appear in a Dolls' Festival parade that her local shrine holds every year. When construction work unexpectedly causes a last-minute detour, it leaves the participants wondering what went awry.