Maybe the break up might have been bc of their age gap, there might have been more things that led up to the break up too. There's nothing wrong with age gap, but i mean she was like 18 and the teacher was probably in her 20s? Maybe one of them was still closeted or they might have not been ready for a serious relationship. Since this is based off a true experience, perhaps the mangaka probably didn't want to include too much on what led up to the break up? Overall, i think it was a nice read ^^