Amano, who returned to the city where he lived as a child for the first time in 10 years, meet Yukio Sawatari, a childhood friend on the first day of transfer, when he (a male friend) turned female! Although she shares her joy, as she suddenly turns into a girl and cannot hide her embarrassment. Yukio was affected by an illness like 100,000 other people, suddenly becoming a girl so-called " spontaneous isomerism metamorphosis ''!