Talk:Kishou Arima/@comment-103.14.63.14-20150319190728/@comment-24494906-20150321220224

^ Eto and Arima didn't fight before the battle in the 20th ward, as far as we know. Yoshimura and Arima did.

However, there is some implication there that they know each other. Eto talks as if she knows him and the title of the chapter reads "play" or "acting" - their fight might have been just an act. (She complains, though, that he doesn't show any mercy.)