Read "Middle School" earlier and just assumed the Japanese school system was different. Now that I know that the child character is a 12 year old, this is pretty fucking gross. Before I thought she was 16, which is still bad, but a 16 year old is at least conscious to some extent with these things, 12 though? That's just gross.
I understand that the teacher is conflating the mother and the daughter, but it should still be an extremely repulsive thought. I also get that the art style can't really portray age well beyond a short character is likely young, or confused to be young, so to the reader it's not immediately apparent. Regardless, it's worrying to me that the author thought up a story where a 12 year old falls in love with their teacher, and it's not seen as puppy love, but something actually romantic. A 12 year old can't understand those complex feelings, their brains aren't fully developed.
Maybe later in the story the author addresses these things, and it all wraps up nicely, but i'm just gonna drop this instead of holding that hope. Final thought: Gross.