Puberty Syndrome—a rumored, mysterious syndrome that only affects those in their puberty. For example, a bunny girl suddenly appeared in front of Sakuta Azusagawa. The bunny girl's real identity is Mai Sakurajima, a teenage celebrity who is currently an inactive high school senior. For some reason, her charming figure does not reflect in the eyes of others. In the course of revealing the mystery behind this phenomenon, Sakuta begins to explore his feelings towards Mai. Set in a city where the skies and seas shine, Sakuta unfolds the meaning behind his bizarre encounters on women with the said syndrome.

My childhood friend Shida Kuroha seems to have feelings for me. She lives next door, and is small and cute. With an outgoing character, she's the caring Onee-san type, this being one of her greatest strengths. ...But, I already have my first love, the beautiful idol of our school, and the award-winning author, Kachi Shirokusa! Thinking about it rationally, I should have no chances with her, but, while walking home from school, she only talks to me, with a smile even! I might actually have a chance, don't you think?! Or so I thought, but then I heard that Shirokusa already has a boyfriend, and my life took a turn for the worse. I want to die. Why is it not me?! Even though she was my first love... As I was drowning in despair and depression, Kuroha whispered. —If it's that tough for you, then how about we get revenge? The best revenge ever, that is~