I don't mind these love rivals. It's rare to have love rivals that are genuinely decent people not trying to get their love interest through deceit and passive aggressiveness (with the exception of the Uka double, who maybe shouldn't count as love rival since she wasn't even in love with Kai, she was jealous of Uka's shine and success, not of her relationship with Kai).
I don't think we've had a genuine love rival either, nothing really happened with Serena, she was there more to help Uka advance her desires than to be an obstacle, but really her story was over before the manga started (SerenaxRio all the way btw). Takamine (is that his name? Kai's hot dark haired friend who's shady) may or may not have made moves, mostly he looks like he's trying to get a reaction out of Kai or like he's the one who knows the most about Kai's circumstances, but that storyline is in it's early stages at best. There was that third year bully who fell for Uka, but all he did was give her flowers and fuel class gossip, he's graduated by now, I think, so who knows if we'll see him again. And then Kai has plenty of anonymous admirers, but really I think this might be the first real love rival... I'm looking forward to this.