Kouki had been out of the series too long - the last time he appeared was a cameo in Subaru's debut fic, Dirty Angel. And Subaru really does need an objective sounding board - someone who can be a big brother to him, rather than a member of his harem. As for Uruha's announcement - it's not a huge surprise, because it's something that's been mentioned before, but it's going to become official, and it will make some people very happy!