What they need is reassurance, trust, and communication. So they can work out their relationship. If they can't do that then they are going to be toxic
At this point, that is not going to work. It’s been a wash, rinse and repeat cycle with them two since Kanghee has been introduced. It can’t become toxic if they aren’t together. It’s toxic that they are the way they are now which is why he wants to break up. He’s tired of it all.
Saikawa should express his jealousy properly. The ex is a bitch