On other manga, I would call this a filler-Fan service chapter, but this is no other manga. If the series really want to go for a serious path, this was a necessary step. The fanservice has a meaning here, showing that, albeit subconsciously, the teacher see his students as women, the twist is that the second he actually starts thinking like that, all his relationships will crumble. I like this story, I feel the way everyone has problems and doubts, and they try to fix them, even if they don't know how. It feels very humane. At the same time he is still a teacher, and the girls are underaged students, it's nice that that fact is not avoided.