Shuko Kodakamine has dedicated the majority of her life to martial arts. Upon entering high school, she tries to leave her past hobby behind in hopes of becoming more feminine and experiencing love like her peers.

One day, Kodakamine nearly collides with the charming Masaki Serizawa who leaves a strong impression on her. It prompts her to ask around about Serizawa, only to learn that he supposedly stole someone else's girlfriend! When he gets into a heated fight with the jealous boyfriend of the taken girl, Kodakamine instinctively protects Serizawa and helps clear up the misunderstanding.

Serizawa, anticipating future problems due to his popularity and seeing Kodakamine's strength firsthand, asks her to become his bodyguard. Though it is not the high school life she expected, Kodakamine's time acting as Serizawa's protector allows her to discover different parts of herself, as well as the pleasant sides to the mysterious Serizawa.