A middle school boy who dies at the beginning of the series (in the manga he was hit by the station wagon Flandre is driving, whereas in the anime he is hit by a falling iron pillar). He finds himself in Hime's service as he is bound to her because her blood (flame, in the anime) revived him. Though young and not very strong, Hiro manages to assist Hime (mostly by being a human shield) through his "half-immortality" that was given to him after his resurrection. At first, he is rather involuntarily involved in the battles but as he learns more about Hime, he is willing protect her. His body changes in the manga when Hime's life is in danger which was left out in the anime.
In the anime episode 24, Hiro realizes he has developed feelings for Hime and tries to kiss her, but she smacks him in the face, not because she didn't want him to kiss her (this is uncertain), but because the gang was watching them, a theory made from what Reiri said in that moment: "You're too slow, Hiro."