Doumyouji didn't say anything to Edward's comment about Tokyo in the summer. He only spent his summers then when he wanted to; he had the funds and means at his fingertips to travel anywhere should he want to. As such, whilst he wouldn't say that Tokyo was an unpleasant place to be in the summer, he could think of nicer places to be. And then, of course, there was the ever present fact that he wasn't in Tokyo and had no way of travelling there, and being reminded of the fact was not helping his mood in the slightest.
Doumyouji's expression flickered as the other boy sighed. He was even noisy when doing that. "Public libraries are quiet. People don't talk in them", Doumyouji commented, eyes flickering towards Edward briefly. Rui was more often found in libraries than he, himself, was, but he wasn't ignorant of the conventions, particularly when they suited him and his mood.