Long story short based on the notes of the author, this is during Mai's middle school years, he stated that customs in rural areas always lead to bad things in r18 manga's. Based on page 13 there's a punishment for having intercourse with a woman who has not yet started having cycles since intercourse is intended for procreation only not out lust.I didn't google translate most of the pages but it Mai still hasn't started her cycles when they had sex, the dude might have had his dick cut of or worse killed because he went against the rules of the village(Which is likely since we dont see him anywhere and Mai probably lost her emotion because of it).
You can just think of this story as an alternate story if you want, since there would be no continuation it seems author wanted to end it in a happy way, he wont be showing the ugly side of the village since we kinda already saw what the people there are capable of in the first edition of the ending the new MC on that one literally got his head lopped off by the villagers looking for Mai.