The story follows a boy named Techno, who spent most of his life in a bomb shelter. He and his grandfather are remarkably intelligent. One day, Techno spots a girl named Hitomi in his yard and instantly falls in love. He calls her Daisy, despite her repeated insistence that it is not her name. After three months of practicing on a robot, he decides to pursue a relationship with her, though he can only manage to stare. He then attempts to claim full ownership of her, yet she still does not truly belong to Techno. During this chaotic relationship, Techno's genius nearly kills Hitomi on multiple occasions. These incidents include enlarging her to 50 feet tall, creating a substitute teacher that fires laser beams, generating a giant slug, and kidnapping her, among other events. Additional bizarre elements involve a teacher in strange costumes, a harmless boy rebel whom Techno, his mother, and his brother want dead, Techno's overprotective grandfather, Hitomi's friends, an android seeking Techno's death while protecting Hitomi, two missiles that Techno befriended, and the rest of the class.