Stop worrying about it, the author baits us with old ass tropes in romance mangas all the time. Wouldn't you think Rio would avoid a cafe with an Ex to put a ring on? It's probably an old co-worker she owes money to and hes held a grudge since then or something dumb and silly like that.
@myfoobz Pretty sure its just you my dude. He was just stating something tons of others already theorized. Not sure why or how you found rascism in that (a word that means literally nothing because people like you)