Zangetsu

Zangetsu is the spirit Ichigo Kurosaki meets inside his own inner world, an unshaven man in a long black coat who stands on the side of a skyscraper and speaks in flat, patient advice. For the first half of the series he is presented as the soul of Ichigo's Zanpakutō, the source of everything Ichigo can do and the voice that talks him through each escalation.

He is not. He is the manifestation of Ichigo's Quincy powers, inherited from Masaki Kurosaki, and he had been suppressing Ichigo's Shinigami side from the inside for years. His reasoning was that a boy who never awakened as a Shinigami would never have to fight, and would live. Every time Ichigo hit a wall and Zangetsu refused him, that was the reason, and Ichigo never had the information to understand it.

The other half of the arrangement is the white figure Ichigo calls his inner Hollow, who turns out to be the actual Shinigami power. During the Dangai training the two spirits merge, producing a form with the Hollow's white coat and horn against Tensa Zangetsu's frame. When the truth finally lands, Zangetsu asks whether Ichigo can forgive him for holding him back, and Ichigo tells him he is part of him and always was. The blade Ichigo carries afterwards is built from both of them.