Chapter 23

Humid Time (湿気の時間, Shikke no jikan) is chapter 23 of the Assassination Classroom manga.

Short summary
The rainy season begins in class 3-E with Korosensei's head swollen from the humidity. After class, Nagisa, Kayano, Sugino and Okano notice Maehara hanging out with Kaho Tsuchiya from class C. With Korosensei spying on the couple, all is well until a group of boys from the main school led by Seo show up. Kaho shifts her blame of adultery on Maehara for being in class 3-E. Maehara tries to defend himself, but the boys start to beat him up before Asano arrives to settle the dispute, albeit still expressing his discontent for Maehara. As the boys and Kaho walk away from Maehara, the class 3-E students approach and consider that maybe they'd end up like Kaho too if faced with a weak opponent. Korosensei appears and resolves to get back at Seo and Kaho with even greater humiliation than they gave Maehara.

Long summary
With the beginning of June, 9 months away to kill Korosensei, comes the rainy season.

Inside class 3-E, the students quietly notice Korosensei's inflated head. Finally, Ritsu asks him why his head is 33% larger than usual. With a poker face, Korosensei explains that his head absorbs moisture from the humidity, to which the students exclaim how similar it is to uncooked rice. Squeezing his head small, Korosensei claims he avoided all the raindrops on his way to school, but can't do anything about the humidity. He also notes that the old school building is deteriorated, hence buckets on the floor catching water from the ceiling, whereas the main building doesn't have this problem and is air-conditioned. Hinano Kurahashi notices that Korosensei's hat is a little loose, to which Korosensei reveals that his hair has grown, that is, a mushroom. Eating the mushroom, he encourages the class to keep a high spirit in the rainy days ahead.

Later, walking down the rainy street together with Nagisa Shiota and Hinata Okano, Tomohito Sugino begs Kaede Kayano for one of her strawberries on her sundae. Okano notices Hiroto Maehara hanging out with Kaho Tsuchiya fromo Class C, to which Sugino admires his popularity. They notice Korosensei behind a tree jotting down Maehara's relationship into a notebook. Sugino notes his love of gossip, to which Korosensei claims is a teacher's duty. He tells Sugino of his plans to release a non-fiction novel of all the students' love stories by the third semester, the first chapter of which will include Sugino's feelings for Yukiko Kanzaki, which never seem to reach her. Irritated, Sugino vows to kill him before he publishes it. Nagisa reflects that Maehara's chapter would be long, considering he's popular with girls and changes constantly within them. Seeing Maehara pull Kaho away from a puddle, Nagisa notes that he's a good-looking guy who's also into many sports, and that he'd probably be more popular if he went to a normal school and got better grades. Suddenly, Kaho notices a group of boys from the main school led by Seo and pushes Maehara away from herself. Seo grows wary of Kaho, who tries but fails to explain herself for hanging out with Maehara. Maehara steps in and reveals Kaho's intentions of keeping him around while his new boyfriend Seo was busy, noting that she barely answers his phone calls anymore and that she switched from biking to taking the train to school. Before Seo starts to lash out at Kaho, she turns around and shifts the blame to Maehara for falling into class 3-E, explaining that she wouldn't even need to see him again once they graduate into Kunugigaoka High School while class 3-E drops out. She claims she didn't say they've broken up, but that Maehara should've known anyways, to which Seo claims he's too stupid to know. Angry, Maehara tries to discredit them, but Seo kicks Maehara down and reminds him it doesn't matter anyways because they won't be seeing each other once they graduate. The group of boys start to beat him up while Seo demands he apologize for sharing umbrellas with her. Sugino starts to lunge at them, but a voice calls for everyone to stop.

Stepping out of a car, chairman Gakuhō Asano tells the shocked boys to stop the violence. He hands Maehara a handkerchief and smiles telling him he was close to getting removed from the school. Asano then bids the boys and Kaho farewell, leaving one of them to admire him for getting his knee wet and giving Maehara his handkerchief. The boys resolve to leave Maehara alone for the chairman and Kaho tells Maehara never to look at her again. As the boys and Kaho laugh and leave, the four class 3-E classmates show up. Maehara laments at how the chairman can settle things with unchanging discrimination against their class. Sugino exclaims that Kaho is a bitch, then hesitates realizing their class has one too. Recalling her appearance in an ad for acne, Nagisa clears him by assuring that Bitch-sensei is a professional bitch, while Kaho is not. Maehara claims he doesn't care anyways because his feelings for girls change constantly. Okano hands him another handkerchief, disgusted at his philosophy as a third year junior high student. Maehara then reflects on Kaho's behavior, transforming from a guilty "excuse mode" to an "attack mode" against Maehara as a class 3-E student, with a sense of immunity from the wrong no matter what insults she'd toss at him. He worries that maybe he'll end up like her if he were faced with a weak opponent, leaving the others to wonder if they would too.

Suddenly, Korosensei emerges with a extremely swollen head. Smiling, he calls for everyone to retaliate for Maehara's unreasonable humiliation. Squeezing his head again, he claims the powerless would accept the situation, but that they are all strong and have an assassin's power of killing a target without being noticed or leaving proof. As the others come to realization, Maehara laughs and asks Korosensei what he's scheming. Korosensei plans on giving them even greater humiliation, to which the others give an evil smile mimicking his own, while Maehara is left a little relaxed.