It’s not that she’s weak It’s like what you said ‘has a reason for acting the way they do’. Don’t you remember from previous chapters? Neko has isolated her from everyone making it easier to manipulate her thoughts because no one is around to point out what’s wrong. Her uncle and basically everyone doesn’t do anything to stop what neko is doing. All her life she’s been molded into neko’s invisible cage. It’s really hard for someone to realize what they’re doing wrong when all their life has been revolved around them. It’s not that she’s weak, it’s neko’s manipulation and abuse that made who she is today. Koito is what you call a tragic character. Neko and koito have a toxic relationship and no one is stopping it. Samon does a bit but not enough to make koito realize what is happening.
Koito is really disappointing. She just learned that Neko blackmailed friends that treasure her, and now she’s going to avoid said friends ultimately because she feels sorry for the creep and prioritizes him? What the hell. Everyone has reasons for acting the way they do. That doesn’t mean that harmful behavior should be overlooked. Samon deserves to be with someone better.