Shuu's so, getting to marry his female best friend! But I'm sure he never expected that it was the girl who approached him before, so it feels weird. But I'm sure Yuika's gonna show her female appeal soon, seeing as they're happily married in the prologue.
Shuu has a rather cynical look on life, but as a son of a businessman, it makes sense. He's ok with making friends, but because of who he is, he knows it could lead somewhere else. He's ok with having someone else control his life too, it seems. But for once, that might have been the best idea here!