Otowa is a drag queen-looking user of assassin's weapons that he has hidden all over his body. He claims to have thirteen total, but he only uses four during his manga existance. His battle tactic is to outwit the opponent and catch them off guard with his hidden weapons as opposed to simply overpowering them.
Otowa is a sadistic individual as he loves to kill people and is not above killing women and children. He is also somewhat of a coward as he plans to retreat from the Kamiya dojo attack after seeing Kenshin glare at him. Otowa was the friend of the shadow ninja Nakajo, who he had nightly competitive killing sprees with. Because of Nakajo's death fighting Hitokiri Battosai, he joins Enishi's Jinchu campaign, but we later see that he really joined the fight just for pleasure.
Otowa later fights Yahiko in the attack on Kamiya dojo. He comes close to killing Yahiko with a few of his weapons, but Yahiko eventually defeats him. As Otowa goes down he has a crazed smile on his face as he couldn't believe his defeat at the hands of someone not even half his age. He was arrested by the police afterwards.