Committing a Cardinal Sin

One day, while Houtarou was in class, the lesson was interrupted by a sound of commotion from Eru's classroom. He doesn't pay much attention to this. However, some time after, while being in the club room, Eru, Mayaka and Satoshi engage in the debates about the relevance of the Seven Deadly Sins to society and humans themselves. Having heard Eru's voice during the class commotion previously, Houtarou asks Eru what the commotion was about and why she got angry during the it. Eru tells Houtarou that the commotion was due to the class's teacher's misunderstanding. However, Eru's curiosity is fired up with the fact of the unknown reason which caused teacher's misunderstanding. To satisfy Eru's curiosity Houtarou starts new investigation.

Plot
During the fifth period of class 1-B, Houtarou sits bored at his desk as the teacher is teaching History. Suddenly, a loud banging of the wall from the class next door halts their class. The teacher in charge of the other class is Omichi-sensei, everyone from class 1-B is interested in what is happening to the class of section 1-A. Yet, as usual, Houtarou does not take any interest in it; until he hears the voice of a female student in that class starting an argument with Omichi-sensei. Houtarou notices that it is Eru's voice, but as the banging and arguing stops, the whole of class 1-B goes back into silence and their class continues.

After-school in the Classic Lit Club room, Mayaka is clearly upset at Satoshi, since he had left Mayaka out in the rain without contacting her, even though he was the one who wanted to meet up with her. As Mayaka tells Satoshi off, Eru tries to stop her, but is unsuccessful. Houtarou tries to avoid intervening, but when Eru starts to silently plead him to help out, he gives in. Houtarou simply tells Mayaka to have a breath, which she agrees to; thus ending her and Satoshi's argument.

As Mayaka sits down to rest a bit, the topic of their conversation goes on about how each member is when they become angry. Mayaka obviously has a short temper and starts ranting. Satoshi on the other hand, though it may not seem like it, does become upset, even though it is noted that his anger is not as wild. Everyone believes that Houtarou would never be upset, Houtarou gets upset about their comment on him, but only in thought. The main subject of the conversation then becomes Eru, everyone is convinced that she has the most tolerance for becoming upset. The conversation shifts to how Eru has no features of the Seven Deadly Sins: Anger (i.e. Wrath), Sloth, Gluttony, Pride, Envy, Greed and Lust; Mayaka and Satoshi are clearly making fun of Eru as mentally stated by Houtarou. Mayaka then comments at how Eru is like a Saint and makes a joke about her name being Angelic as well; Eru gets upset and firmly tells them to stop. Mayaka and Satoshi then comment that having any of the Seven Sins is bad, but Eru disagrees and tells them that the Seven Sins are actually essential. Without Pride, people will have no self-confidence, If there is no Greed, people wouldn't have the wish to bring in money to support their families. And without Envy, nobody would have the desire of creating new objects that could surpass others.

Forgetfulness by the Self-Strict Omichi-sensei Case
Omichi-sensei is a maths teacher who teaches classes 1-A to 1-D. He's usually a strict person on others and himself, and is always cautious, going as far to check the classroom name and number before entering the classroom. Yet, one day, during fifth period, the maths period Eru is in, the teacher asked the students to find the "range" for a quadratic equation, even though Eru's class haven't learnt it yet. The teacher shouted at the students for not knowing the concept, yelling and ranting. Finally, when Eru stood up and advocated whether or not her class was really on "range" topic, the teacher realised, then apologised and corrected himself. The class thereafter returned to normal. Why would such a cautious teacher make such a simple mistake about how far the class has gone?

Solution: Because of the way most maths teachers write their letters, Omichi-sensei wrote his notes of which class is on which subject in lower case. Therefore, the "a" and "d" looked similar confusing him.

The Anger of Eru Chitanda Case - Part 1
Eru was upset at what had happened during her maths class with Omichi-sensei, yet she doesn't understand why she got upset. Very kind and very much like a saint with no sins to the club, she usually wouldn't get mad on such a minor matter, yet she did. What was her reason in getting upset?

Solution: Houtarou had a thought that Eru might just want to believe that there's a reason to Omichi's mistake which makes him angry. But, since he doesn't know Eru that well, he'd chose to leave it at that since that would mean he is arrogant to believe that he could predict everything about her.

Trivia

 * This episode is adaptation of Story 2 "To Commit A Deadly Sin" from.
 * The book Houtarou is trying to read during this episode is Summer Calamity (夏の災厄), written by . Specifically the 1998 edition, which is consistent with the time in which, at least the novel, takes place.