Ittōsai Kunieda

is the grandfather of Aoi Kunieda and Kōta Kunieda.

The master of the shingetsu style and Kunieda's instructor, he is a strong old man who sports long white hair and a moustache. He has a violent personality and, on meeting Oga for the first time, drags him to a brief spar, and is actually victorious. Seeing potential in Oga, he offers to train him if the latter wants to become stronger.When Oga decides to take his offer, he smiles mischievously and begins by ordering Oga to perform a number of household chores, to his great dismay. Later he takes up Teimou's shadow group and leads them all into a training excursion, first ordering them to break stones with their bare hands. He is a very stern man with a hair-trigger temper, and adopts an attitude of fighting first, asking questions later.Not only does he know about demons and the demon world, but he also recognises Oga as a contractor and decides to train him to use demonic powers. He engages Saotome's assistance to this end, much to Oga's dismay. It seems that the three adults who know of the demon world so far - Grandpa, Saotome and St. Ishiyama's Headmaster - are somehow connected.

Abilities
Ittosai is the master of the Shingetsu style and can perform every technique it emplores. He taught Aoi and the Red Tails how to fight. He also showed no fear when facing off against Behemoth.
 * Nadeshiko - A stone breaking technique which he taught to Oga and Aoi.
 * Kannagi - (Eighth Ceremony Sword drawing technique) Ittosai unsheaths and resheaths his sword quickly causing the area where his target is to be cut compelety in half.