So basically three elementary kids

two boy and 1 girl, boy A was naughty but cheerful , boy B was quite silent , cool and calm type

The girl was a kind/happy type

Three of them play snowball on field. Boy A try a prank by putting a stone on the snowball and throw it to the girl. It hit the girls heads and her head bleeding badly. All kids and people there are shocked and panicked seeing the girl bleeding. In panicked state, Boy A was blaming boy B by saying that he put a rock on the snowball.

Boy B try to denies it but all the kids there got swayed by boy A opinion and he got blamed so bad.

Later the girl left ear got damaged badly and she can't hear anything at her left ear

People then bullying boy B so bad , to the point that boy B because a very cold and lone wolf person, he does not have any friend till high school and people/teacher keep thinking him as bad person.

Boy A was feeling guilty and decided to avoid both the boy B and the girl

the girl was also feeling guilty, she know the truth that Boy A was the culprit. She try to calm the mass by telling people to not bully boy B, but they still bully boy B. In the end the bully stopped at middle school but they now play a "avoid this person bully", nobody try to help/approach boy B.

Boy B was becoming cold , and have this lone wolf aura so basically he avoiding people and people also avoiding him. Three of them did'nt attend same middle school but they attend same high school later.

The girl then somehow try to mend their relationships in high school but boy B always avoiding him after their reunion. The girl persistently and managed to open the guy little by little, she also try to approach boy A to clear their sad past.

In the end the girl managed to invited two of them to her house(her parents are busy with works), and boy A in awkard moment say he gonna go to convience store to buy drinks. The girl burst in tears after boy A left and apologizes to boy B, they got in heat moment and having sex.

Boy A was coming home, shocked and say ah sorry to disturb you, take his bag and wanted to leave. Girl then grab the boy A and somewhat talk to him about the snowball incident.

I think in the end three of them managed to clear their past remorse, three of them then begin walking together to school, the last panel also changed when three of them still kids and walking together and the girl say "at last three of us are together again "

i will admit ,this is very hard to find, because the manga was only 1 volume, it was one-shot story,there are several on shot story in 1 volume of that manga.

welp that's it, i hope someone know this manga, it was quite a good read to be honest,