I generally like this series, but I don't like this chapter at all. I don't know if he's supposed to be protective or jealous, but it's not a proportionate action in this situation, and just makes him seem controlling. Let the girl wear her swimsuit.
Just to let everyone know: mangadex's uploads are way behind, so you might want to go looking for the missing 12 chapters, if you're impatient like I am.