9th Period 'Collarbone' / 10th Period 'Library Room' / 11th Period 'Lifting Skirts' / 12th Period 'Experiment'.Ryöta claims that collarbones are the best female corporeal quality in order to divert attention from himself when the boys of the class demand that he justify to the girls why guys like gravure magazines. At the end of school in the park, the girls and boys gather in their own individual groups to reflect on the matter. After Ryöta and Köji are dragged to the library by Tsukasa, they encounter Chika who requests Ryöta's shoulders for a vertical boost. Because she fools around, Ryōta loses his balance and the two crash on to Kazumi. Seeing Köji use a chair as an aid, the two launch into an argument over who is to blame for their accident. A pair of underclassmen boys rushing by to flip Yüki and Chika's skirts prompts the question of when children begin to exceed the age limit for excusing that kind of behavior. When they ask their friends, they receive many different and end up finding out to their disbelief that Ryöta has never flipped a girl's skirts before. Later, Chika decides to play a prank on Köji by accidentally leaving a recently-purchased skirt on his desk. After the incident is resolved, Köji suggests that they attempt this prank on Ryöta.