Here he says that he is indeed Kaien and even addresses Rukia by name and then..the weirdness begins....first he tells her how his soul cracked and he ended up being sent to Hueco Mundo along with the Hollow that had originally possessed him. He eventually ended up taking control of the Hollow's body and joined the Espada to get his revenge on Aizen. Then he asks Rukia for a favor, something only she can do for him....and then he slices her across her cheek with his Zanpaktou in a flash....
This is about when the real confusion begins....At first he tells her that she needs to be killed by the man she once killed to atone for her "unforgivable sin" which she agrees upon, on the condition that she has to save Orihime first and then he can kill her. He says he's joking. The second time he says that he'll let her go if she does something only she can do for him...bring him the heads of her friends.....