Talk:Kishou Arima/@comment-10733658-20160625130440

So theory time:

Arima went into this battle knowing only one of them would be able to survive. And he fully intended to die during this battle. That's the reason he's spent the entire battle either taunting and threatening Kaneki, or challenging whether he really wants to die, or pushing him harder to fight. It's why he didn't finish Kaneki off, all the chances he had and instead kept pushing him to get back up.

This chapter, he informs Kaneki that the battle doesn't end until one of them is dead. But I don't think it was merely Arima's stubbornness, and simple pride or refusal to give up. Because once he realizes he no longer has the strength to force Kaneki's hand, he just....deflates. He stops fighting, and instead talks about having no more options against Kaneki. So once he's absolutely sure of Kaneki's decision, he kills himself so the requirement of the battle is fulfilled.