Yes, the blonde is the ML. The other dude in the cover photo just appeared in this season, but they just talked a few times for some specific reasons (no spoilers from the main plot) the MC is in love with the ML and he doesn't have eyes for anyone else, same with the ML (he's crazy about the mc, crazy for real) It's just the mc is a little dense so he doesn't realize the other dude is interested in him but even so he would still chose the ML he just love the person inside that body.
I can't really remember when they started dating but it was kinda a slow burn, the kissed and stuff but they waited to graduation I think... not sure it's been a while
Is this a love triangle?