Frog Fangire

Using a sword & a rifle, the Frog Fangire can fire energy warts on his shoulders. In 1893, Duncan created the Black Star violin, attacking any he found not to have respect for his creation. He attacked Lillian Walker for that reason before being driven off by Garulu. Later, Duncan encounters Jonathan Harker after he stole the Black Star from Lillian, with Jonathan's music soothing Duncan to see Jonathan as a worthy owner in spite of Jonathan turning him down. However, Jonathan has Duncan promise to not feed on humans again, helping him escape to start his life anew with the disposing of the Black Star as the first step.

In the present day, Duncan keeps a music player that plays Jonathan's music, a calming mechanism to keep him from breaking his promise. However, while taking a break, Duncan is driven into a frenzy after hearing a rock group & lashes on them before fighting Vampire King, the both exposing themselves to the other. After Scott saves him from Keisuke Nago, Ōmura reveals what happened in the past. However, Keisuke refused to accept it, provoking Ōmura into attacking people with Kiva almost forced to kill him. Though Ōmura regained his senses and ran off, he was found by Keisuke and mortally wounded by Ixa's Ixa Judgement. By the time Wataru arrived, Ōmura apologizes for breaking his word before he dies.