Prince from an alternate dimension that is running from Lord Kumagai, his uncle who wants to be king, by using objects called the Absprung and Himmelskarte.
Kriss S. Sison, artist of the book, came up with earlier designs of Hiroto that made him come off as too dark and gloomy or too drab and commonplace until he finally reached the design and look Hiro has in the book.
"He comes across as a brooding, sullen and quiet young man, yet seems to have an inner fire burning within. In his own land, he was a prince, and should have a certain noble regal bearing about him. Yet some of the kids mistake his sense of nobility with arrogance and resent him for it.Girls can't help but be intrigued by his air of mystery, but he wants nothing to do with them, or with anyone else, for that matter. In fact, his attention always seems to be somewhere else."