On the first day of summer vacation, Kanako Miyamae is visited by her beloved younger sister, Miki. Kanako just wants spend her vacation lying around doing as little as possible, but Miki unveils a shocking secret. Reeling from Miki's confession, Kanako exposes Mariya's secret. And to complicate things, Ryuken Ishima's fiancé pays a visit to the school! And the fiancé is... an elementary school student? The tense romantic comedy between a refined girl and a cross-dressing sadistic boy continues in volume 7–the summer vacation!