Ryuuta Bellemonth (竜太・ベルモンド) is the main character of the fanfiction The Worst Intruder written by Mogami Kumagawa on fanfiction.net. Ryuuta is an Invader, a type of character in-verse that is foregein to the DXD world but enteres it to change various things about it. For some unknown reason, the canon characters are aware of his status as an 'invader', even when time and space shouldn't have allowed it.