[Smooth, Yamaguchi. Smooth. But his attempt at covering his mention of Kageyama is almost sweet in a way. He cares about Oikawa's feelings regarding Kageyama enough that he'd blurt out something like that.]

Yama-chan. You're allowed to have friends. I'm glad that you had someone else to call. [Sort of. He's sober and older than Yamaguchi so he can't very well say that he'd rather Yamaguchi stays far far away from Kageyama before he becomes a better person as well as a better setter than Oikawa. But he wants to.] But I am better company, aren't I?