it's normal for people with one sided love to put some distance at some time if they think their feelings will never be reciprocated. and that's exactly what sakura did so he didn't really have to apologize to mizuki when he didn't do anything that he should feel sorry about
I think he wasn't apologising for protecting himself but for hurting Mizuki in doing so. I agree that protecting oneself is necessary and we really need to see more of that in mangas. I think this is one of the few ones I have seen someone actually putting distance after a hurtful thing. But I'm still not sure that here putting distance in such a way was the right thing for either of them. Mizuki says so, that letting him feed send mixed signal to him and I don't think that it was doing Sakura any good either. Communication was still needed for closure on this issue and the particularities of this relationship made it glaringly obvious that closure was needed for both of them. What Sakura did, while trying to protect himself, hurt Mizuki and didn't quite help him so it felt kinda wrong to me. Had he broken things off entirely or put some actual distance and try to communicate, both of them could have had closure on the issue and decide whether to move forward or not with the relationship instead of what happened of one starving and the other worried about a guy he thought was just using him and making him feel worse.
i'm so glad when sakura decided to break things off with mizuki. well, not entirely. but he tried to put some distance between them to protect himself. i know mizuki can't help it since he really needed a cum that badly, but it still puts me off. so im really glad when sakura did that instead of brushing it off like it's nothing. but i dont like how sakura apologized to mizuki saying he's sorry because he was just trying to protect himself and did not consider mizuki's feelings. i mean, there's nothing wrong with protecting yourself??? and sakura thought that mizuki doesn't have feelings for him anyway since mizuki never said he liked him (at that time).