Y/n discovered that his sister Ikaruga considered him a Burden, that she slowed her self down so that he could catch up in training, and that he was adopted. Everyone else thought similar thought or were uncomfortable that he was a boy. He felt out of place, and left, he ran away.

He's Kidnapped by a Cultist group, and used in a Sabbath, however, his Despair turns to unbridled rage, his life had already been ruined enough by Shinobi Hypocrites, HE WOULD NOT DIE IN SOME MAGIC BULLCR*P! He seals his Phantom inside him, Pheonix. Kamen rider Wizard arrives and stops the newly turned Phantoms, but gives Y/n a chance of redemption as it were to use his new powers, becoming Kamen Rider Rizer.

He's gonna take care of the Yoma... permanently. And show just why Kamen riders are heroes, Shinobi are just a thing of the past.

He was once best friends with Hibari when they were kids, then Yagyu came into the picture, pushing him further and further away from Hubari, at one point he had to move, and wanted to spend one last day with Hibari... she never came, and Y/n never considered her his friends again.