Kokoro Katsura, younger sister to Kotonoha Katsura, lives with their affluent parents. By day, she works competently as a waitress at Radish Restaurant alongside colleagues Sekai Saionji, Hikari Kuroda, and Nanami Kanroji, though she visibly bristles at what she considers patronizing praise from her sister. Kokoro secretly leads a double life as the magical superheroine Magical Heart. Commanded by Youko Saionji, she operates from a hidden headquarters accessed via the restaurant's locker room. In this role, she defends the city, combating threats like a virus transforming citizens into perverted zombies, using spells to reverse transformations and displaying significant combat prowess. While initially supported by the Radish Mobile Squad, their failures sometimes necessitate her direct intervention. Overwhelmed by Doctor S's enhanced henchman during a major confrontation, she is rescued by Makoto Itou. This event leads her to team up with another superhero, Magical Word (later revealed as Kotonoha). Together, they combine their powers to summon the mecha Mayo-chan and execute the finishing move "Bloody Conclusion" to defeat their enemy. Kokoro maintains her secret identity, deflecting Makoto's attention when he notices her resemblance to Magical Heart. Her superhero equipment includes the life raft "Nice Boat," used during rescue operations.