“But this flower had sprouted one day from a seed that had blown in from who knows where, and the little prince had kept a close eye on the little shoot which was different from other shoots.”
Arima has been wild this chapter, and I guess it’s frustrating that everybody is reading the chapter at face value instead of recognizing what Arima is doing exactly, but I’ll bullet some info:
Arima has been confirmed to be breaking protocol by not killing Haise
Arima has been confirmed to deliberately disobey Yoshitoki’s and Haisaki’s orders, instead letting Kaneki go multiple times and encouraging him to fight
Arima does not want Kaneki to die whatsoever, both in his speech and in the meaning of 645 (x)
Randomly thinks of that picture Ishida drew: I will not permit you
Arima was the one to breach Kaneki’s suicidal tendencies (desires) so that Kaneki will fight to live another day
Kaneki has genuine feelings for Arima. He doesn’t understand Arima but he desperately wishes he could, and he truly sees Arima as a paternal figure
Kaneki was the one who got Arima to appreciate the beautiful things in life, starting with his poem in v14 (x); he’s also the one to get Arima to enjoy the little wonderful aspects of life (such as reading)
Kaneki is Arima’s rose as his role as the Little Prince. Now where’s the fox who will tell Arima this (x)
This is the most Arima has ever talked in an single go. Wow.
Now it’s just a matter of why Kaneki is so important to him
Maybe Arima doesn’t know
Maybe Arima doesn’t want the one good thing in his controlled life to die; the one human aspect of himself that he isn’t able to achieve as a “god”
Maybe he sincerely wants Kaneki to kill him (paralleling Kaneki’s suicidal tendencies)
Maybe he wants to bring out the best of Kaneki since he recognizes his potential