Hiro as Yuzu calls him is the main male of the series. As far as I can tell he contains a secret in his body the masked_man wants. Hiro's eyes are two different colors. His red one bulges out during specific times. Often around the demons or when the demons are active.
Hiro in a way it a bit of a whiner, but for his sake rather the being the perfect hero, he is more or less a burden. If he isn't protected the world may be doomed knowing the way stories are. If he is protected by the mikos they are put in danger. In essence he feels like a burden to everyone.