Do people seriously expect this to be a rival/NTR type of character? Maybe he'll add a bit of drama, sure, but I think people are making too much of a big deal out of this guy. Rinko literally showed no attraction towards this dude. People like him flirt casually all the time, even when the have...
I can't believe that there are people complaining about the lack of intimacy between them and saying how weird that they haven't fucked yet, when every single omake hinted at them just fucking afterwards, which just cannot really be shown in the manga like that.