Spoilers- he's not calm at all. He's just very, very good at keeping composure for the sake of others.

...Which might not be the best thing, but still. "Auh- I- In my defense Yuuya," he laughs a little nervously, "I, the man Gongenzaka, have spent much of my time in here following breathing exercises, meditating..."

Because what else was he gonna do right.