Andy has a boyfriend and he's the replacement, and that boyfriend is being pushed to the edge because Andy and yes Andy is also part to blame but he's also a victim of minjae In this case, minjae doesn't even love him and yet still trying to date Andy knowing the fact that his replacement is in love with Andy
Andy cheated on his FWB which is Minjae replacement, Andy's FWB already has feelings for him(Andy) and but then Minjae "stole" Andy, while I don't blame Andy because he is just his FWB after all with his replacement so he did it with Minjae but then Andy actually fell for him sven though Minjae did it to make himself feel better because his replacement plays better than him, that's kinda what happened from the spoilers I've seen
Uhm...I'm not sure where you read your spoilers but I read the book and Minjae was ultimately a victim. Andy and his FWB never informed Minjae that they were still smashing. Also, Andy had been crushing on Minjae for a long time. Minjae initially dated Andy out of childish spite against the FWB but he did like him and was hurt when he found out Andy was cheating. Minjae immediately steppped out of the picture but Andy wasn't having that. The FWB loved Andy and chose suicide because Andy wanted to get back with Minjae. Minjae actually hurt his arm trying to save the FWB.
As for the alleged simping on Heechan in the past, that's false. Minjae was dismissive of Heechan (just like everyone in their class) because of Heechan's surly attitude. His one main interaction with Heechan was before he went off to Canada, Heechan had runaway from home and he ran into him on the streets and told to go back home to his worried mother.
Minjae developed an interest in Heechan during present times. He did play some games on Heechan in the epilogue to test his love but it honestly didn't feel malicious.
Yeah I read some spoilers and some translation ahead of the manhwa, Minjae (a total bastard) is so insecure with his replacement on the team that he ruined his relationship with Andy and drove him suicidal byeee also he's been obsessed with heecan since forever but he's too much of a pussy to confess that he take it out on others and ruined their relationship