I mean yeah thats the whole purpose of 2nd ML LOL. I hate it and wish it wasn't such an over used trope.
But we already are seeing Luna as a shitty guy. He was following MC online, then preying on him once he finds out MC is on the rebound. Then realizing the ML had feelings too so he pits ML against MC. He's using all the info MC told him in confidence when he thought they were friends, but using that info to manipulate MC and ML instead. He doesn't have MC best interests in heart and it's been showing. Normal guys would wait or help the person they're interested in to move on before swooping and they wouldn't try to meddle either.
So its not big surprise the 2nd is bad news if you can recognize the red flags.
are they gonna pull some luna was actually evil the whole time and shitty guy who never cared now actually does