Haruto Mizuno is a cisgender male high school student in Tokyo who disguises himself as a girl named Haruka in order to infiltrate and understand the world of girls. Outwardly, he is cheerful, friendly, and stylish — a beloved gyaru known for her bubbly charm and fashion sense. Beneath the surface, however, Haruto is calculating, observant, and fascinated by the way people drop their guards when they think they're among friends. His disguise allows him to study social dynamics and manipulate situations to his advantage, though he often justifies his actions as research.