The thing that is bugging me is why did the fuckboi ask shinobu to "Break up with her" after sakura already messaged Shinobu to never see her again and switched agencies. And after his talk when they are both walking away, he does not look happy which he should be if he completely broke their relationship. I feel like something else happened that night that will be revealed later on or maybe he just wasnt expecting Shinobu to give up so easily (which I really hate by the fucking way, your girlfriend just cheated due to a misunderstanding and you are letting it go because she is happier that way? I know he wants to do whats best for her but cmon man)
Re-reading these previous chapters to look for clues is so shit dammit.
If I recall right, they verified there was a verbal agreement between Shinobu and Sakura in being her manager. While there was no written agreement, apparently some past comments stated that verbal contracts still hold weight in Japan.
So with Shinobu agreeing and seemingly Sakura already having done so, it'd completely void the agreement and Shinobu can't act on it. That or it's to also ensure that they don't have Shinobu hinder Sakura in advancing her career. Keep in mind they don't think Shinobu is a good guy because Sakura was quiet when they were bad mouthing him.
Honestly, If I was the fuckboi, I would have been HELLA confused. Like this bitch is opening her legs while in a relationship with someone who is and has been doing everything to save her and make her happy without even asking for an explanation from him, while that same dude sees that his girl immediately fucked another man and is letting that man fuck her because he wants her to be happy. I would've skidaddled the fuck out of this situation thinking that these mfs are not right in the head.
Would you have been though? If you were honestly him?
You're under the impression she's being cheated on. You see her being sad at the thought. You find her charming and cute. Beautiful too like everyone else. You want to be with her but you can't. You suck at romance. You don't think Shinobu is a good guy to begin with.
Then you see her crying after confirming your suspicion that she was going to be abandoned.
As far as I know, Yuma doesn't think Shinobu is a good enough guy if he's doing this. From his perspective he's taking Sakura away from it as you want to try and make her more happy than she was with Shinobu.
It's honestly not hard to see why he acted the way he did. Even if he sucks at romance. You don't know the full story. You only see her side of it.