Thoughts on this manhwa that i read??

Yall probably know this but WHYRE PEOPLE DEFENDING THE MC

Apparently the Mc had a fiance but hes quite literally cheating on her with someone he knew in the past and yet that someone is also friends with the MC. So lets call that someone "bitch" though that bitch doesnt necessarily think of MC as a friend. That bitch knew the Ml is her fiance but had the audacity to send a pic of her to him but he got all horny and decided to go to that bitch so they could fuck. THOUGH ONE THING I HATE the Fl who was bored decided to have a student since back then she was quite famous on playing piano and found a person whos good at it but she kept on blushing with him and yet later on in the chaps she kissed him??? and then thought to herself on why she did that.
She herself doesnt know that her fiance is cheating on her but ISNT THAT STILL CONSIDERED CHEATING??? Theyre both cheating on eachother SO WHYRE PEOPLE NOT NOTICING HER FAULTS?? Though the fl and her fiance still like eachother and yes you guessed it, the title is Lost motion