Kaneki was in a bad state after being attacked by Rize. In order to save his life, Rize's organs are transplanted into him. Thus, unbeknownst to him, Kaneki was turned into a One eyed Ghoul, after Rize Kamishiro's Kakuhou was transplanted into him following the Steel Beam incident. Having a ghoul organ transplanted into him brought about changes in his body, eventually making him an artificial part human- part ghoul.Why did Kaneki become Haise?
Kaneki became Haise Sasaki after he lost his memories about his past . Seeing that he had lost his memories, Kishou Arima came up with a new name and identity for Kaneki (Tokyo Ghoul:re chapter 67). For this purpose, Arima asks Kaneki to choose his two favourite Kanji characters. Kaneki chooses kanji from the words coffee and world, which makes his name Haise.Is Kaneki a full kakuja?
Kaneki's kakuja are twin centipede-like tails protruding downwards from his back with sharp talons on the side. In this form, Kaneki's kakuja forms a mask that features a hole for his left eye and a bird's beak over the middle of his face. They provide Kaneki with enough power to even overwhelm Shinohara's Arata Proto.