
How are you even supposed to know you’re one step away from starting a relationship? He didn’t know that the mc was going to confess his love or anything. The seme had doubts about himself and his ability as a dom. He didn’t want to push the mc because he’s seen how that has played out in the past. Yes, he liked the mc from the start but he didn’t know the uke felt the same until the confession. If you’re fwb with someone, then you sleep with someone else that is not cheating. Now, if they were in an exclusive relationship, then yes, that would be cheating. The uke wasn’t even jealous, he just wanted to let the seme know how he felt.

You can have feelings for someone else and still fuck around with other people.
I carried a torch for my childhood friend for 15 years and still managed to sleep with other people regardless. Not everything is all sunshine and rainbows when it comes to love and relationships, especially as you get older. You learn that most of the time it's messy and your feelings won't ever match that of your partner's.
It's childish to hold onto the "if you really loved someone you wouldn't be able to sleep with anyone else till your feelings are reciprocated" fantasy. First loves have a very low success rate for a reason.

There is a difference between being in a situationship that you want to push forward to the final step and being in a one sided love. I expect that you won’t mess around if you’re serious about somebody. If you sleep around in this situation then it’s your choice, but I would just personally not see a future with a person like that.
ML was about to cheat on MC if he didn’t stop him. This is ridiculous. Bet next time they argue he will look for other people.