I believe it's part of a tankoubon. It takes place in a village cut off from society and they have a coming of age tradition. The tradition is that an adult male marries the coming of age girl.
It starts with the girl running to meet her male childhood friend after her mom helps her put on a yukata/kimono. She is then interrupted by her arranged spouse and they go straight to a private room to get child making. The childhood friend is pissed off because of the messed up tradition and watches the girl he likes have intercourse. It ends with the girl giving birth and the childhood friend mind broken.
There are two twists in the the story, 1st the adult male is the childhood friend of the mom and seeks to inflict the same pain to the girl's childhood friend just as he suffered.
2nd the cycle repeats for the childhood friend as he swears he will wait for the daughter's†‹ coming of age to inflict the same pain he had thus repeating the cycle and keeping the tradition alive.