I'm not saying it the was the right thing to do, BUT:
1. MC and tan dude aren't dating or in a relationship so MC didn't cheat
2. MC was scared pale guy would call tan dude to sleep with him (tan guy totally would since as of now he's in love with pale guy), so MC would rather sleep with pale guy instead of pale guy sleep with tan dude (at least this way, MC has a higher chance of being in a relationship with tan dude)
Wow I thought MC and mr.tan were a couple
The MC did too , but then he realized they never actually talked about it, they kinda just slept together a few times
I still don’t understand why he slept with ah-in, why would he rather cheat than talk to his bf.