I won't say this kind of NTR-ish arc is bad, since rarely it actually works, but this is just unnecessary. If the MC wasn't dating her yet maybe, but there was really no reason to make this arc since they already know they love each other. I would've definitely been better if the handsome dude was just a good friend and just wanted to help so it wouldn't leave a bad taste in peoples mouths. honestly i'm fine with it as long as the guy doesn't get more assertive than he already is. but i mean, its just a drawing we need to calm down.
tl:dr: the arc is kinda unnecesary but it'll be fine long as it won't get dragged out.
thank you for coming to my ted talk