Part 1 Haruka's at school having lunch with her friends where Maki discusses why she wants to resign from school. When Haruka doesn't seriously buy her reason, Maki going underneath Haruka's desk to get her melon bread leads Haruka to take action on her friend.
Part 2 When Kana teases Haruka about doing "naughty things" with a guy at school, Chiaki gets curious over what Kana is talking about and an embarassed Haruka threatens Kana not to explain anything. But when Kana is asked by Chiaki over "naughty things," even Kana gets hesitant to explain anything. The next day at school, talk about a get-together with homework at Chiaki's school leads Chiaki to talk about "naughty things" that gets her male classmates flustered.
Part 3 With her classmates talking of nicknames given to the teachers, Chiaki assigns her own nicknames to her classmates with humorous results.
Part 4 Chiaki's class is cleaning up their classroom where Makoto's attempts to help Chiaki sweep up dust on the floor result in him being forced to carry buckets full of water for the entire day.
Part 5 Kana gets irritated with Chiaki studying in the living room alongside her goofing side. The two challenge each other to answering different questions which gets to a point where Chiaki attempts to get Kana to write an essay explaining "naughty things" to no avail. When Haruka gets home, she also gets dragged into writing an essay on "naughty things."