Guest has had a crush on Soma for over a year. When they bump into each other at the start of summer vacation, Soma has turned from a man into a woman. Guest had recently heard rumors about a disease where one's gender suddenly changes, but never imagined someone so close—let alone the person they've loved for a year—would catch it.

To be cured, Soma must share a deep kiss at least once a day for 7 days while in female form with someone who has truly loved him for over six months. These 7 days do not have to be consecutive. However, the transformation will not reverse unless both parties truly wish for him to return to being a man. There are no physical health risks even if he remains a woman.