In fact, I was wrong about this Ken. He is Part 1 Ken because he cares about his friend, he is strong like "White" Ken and even much more because he is stable. The only difference is that he is more realistic while the others seemed lost inside. Finally, the first and the second can be associated as the current one with Sasaki. Sasaki just didn't have his memories and was kind with everyone, even with opponents he defeated. Then the next step will just be Sasaki with Kaneki's memories for me.