Yoshina Tsutomu (male) woke up one morning to find himself a silver-haired, odd-eyed vampire (female).

According to his foster parent, Tillura, he had been transformed from female to male for a certain reason when he was young, but the effect had worn off, causing him to revert to his original form (gender).

Tsutomu, indignant at the idea of returning to being a woman, pleads with Tillura to change him back into a man, but is informed that it will require some preparation time.

And so, Tsutomu adopts the name Tsukasa and enrolls as a transfer student at his former high school.

This is a story about a person whose life is turned upside down (in a gender-related sense).