Mitsudomoe

Newly hired teacher Satoshi Yabe begins his job teaching class 6-3 and soon becomes aware of the terrible Marui triplets, Mitsuba, Futaba and Hitoha. When the triplets notice Yabe might have a crush on the new school nurse, Aiko Kuriyama, they purposely try to injure his groin in the hope that Kuriyama will like what she sees. When Yabe incidentally gets injured after running into Kuriyama, she confuses him for a fourth grader (she's blind without her glasses). Yabe gets the class a pet hamster, which Hitoha names Nipples and becomes attached to. When others start to play with her too much, Hitoha starts becoming defensive.

Futaba catches a cold and ends up ensnaring Yabe into a rather long and sticky booger. Hitoha gets access to Yabe's apartment in order to see Nipples outside of school, blackmailing him from making other arrangements.

A boy named Yuudai Chiba catches a glimpse of Hitoha's erotic book and wants to see more of it, his friend Shinya Satou getting confused and assuming she wants to see her panties. Through certain events, Hitoha ends up meeting occult fanatic Sakiko Matsuoka, who mistakes her as being able to see ghosts. They end up sneaking into the pool before it opens, with Sakiko assuming Hitoha is trying to exorcise spirits, when she is actually drowning. During swimming the next day, the triplets forget their underwear and jump to the conclusion that they were stolen. When their suspicious looking father, Soujirou, arrives at school with the panties, Mitsuba is too embarrassed to admit losing them and implies he is the thief, getting him arrested.

During an art class, Futaba, who has an obsession with breasts, end up drawing various pictures of breasts, one of which the principal determines is a work of art. Whilst at the triplets' house, Shinya tries to stop Yuudai from playing around with Mitsuba's panties, only to get labeled as a pervert himself. This leads Futaba to believe Shinya has an interest in Mitsuba's panties, and continuously tries to give him large amounts of panties all day. When he tries to stop Futaba, Shinya ends up in another seemingly perverted situation in front of Mitsuba.

After being pressured by her classmates, Mitsuba goes with Futaba to buy a bra. Later, Nipples becomes attracted to the hamster design on Mitsuba's panties, making Hitoha jealous. Mitsuba gets into an argument with Miku Sugisaki over whose breasts are bigger, though ends up in an embarrassing situation. Soujirou is invited to the girls' parents day, though whilst trying to shave his beard to look less suspicious, he ends up shaving all his hair and looking even more suspicious. Mitsuba and Futaba get their essays about their respective feelings towards him mixed up, clashing with his expectations of them.

On the night before the Sports Meet, Futaba decides to rehearse for the event by having Soujirou fill in the other parts and obstacles. On the day of the Sports Meet, Futaba behaves ravenously in a game of piggyback, much to the lament of Hitoha and Mitsuba. Later in class, Yabe collapses with a fever, but when Hitoha goes to check on him, Sakiko is setting up some kind of ritual, which makes things awkward for Hitoha. During class, Miku tries to make Mitsuba jealous of her, but only ends up embarrassing herself.