Kanako will be helping out with the upcoming general health check, but she realizes that Mariya will skip the general health check after she notices him ditching breakfast. In the infirmary, school nurse Tonomura assigns the class and deputy representatives for taking measurements. However, Kanako faints and recuperates after Nanami undresses to take her measurements. Sachi, Yuzuru and Honoka visit Kanako in the infirmary, where Kanako apologizes for her behavior. Kanako passes out again upon seeing Mariya with a real bust. She wakes up and strongly believes that this Mariya is still a boy. When the real Mariya shows up, it turns out that Kanako was talking to Mariya's twin sister Shizu Shidō, who attends the all-boys academy Mihoshi no Mori dressed as a boy. Based on their late grandmother's will, Mariya and Shizu must attend school dressed as the opposite sex and keep their identity a secret, with the prize being chairmanship of both academies. Mariya's secret was discovered before Kanako's enrollment and Shizu's secret was discovered after Kanako's enrollment. After Shizu run out the infirmary in embarrassment, Mariya confides in Kanako that he was using tough love on Shizu. Kanako is later accused of stealing Honoka's black underwear.