Narunosuke is a Tōjū that appears during Beast Swords Arc. He is also the first Beast Sword to reveal his name.
He appears as a young, attractive, thin man with Indigo hair and purple eyes. He wears white and gold patterned guard over his left shoulder with a neck guard protecting his neck's left side also. He has a black snake entangled round his left arm.
 Beast Swords Arc
He is found in a field of red lilies injured by Hainako. Upon seeing his face she is mesmerised and chooses not to kill him. She later finds a hut for him to sleep in and to stay whilst his wound heal. Over several days Hainako brings his first aid, food and drink and she grows affectionately towards him. However he often had intense and severe migraines that slowly graded away his sanity, slowly turning him into a Tōjū.
As he finally transforms, Hainako is the one to end his life as a Zanpakutō.