Definitely had past interactions with Xu. He claims she's one of his childhood sweethearts (her own opinion of him may vary XD). He most likely has been involved with more than a few of Novea's past missions.
Naomi is on his list. She's the first one he calls when he feels like going out on the town, they can tag team the unsuspecting and break hearts.
Irvine will fall in love with Sage at first sight, guaranteed. He'll also offer to teach her how to master firearms, so there is that.