LF Manga Hentai: Fellatio, Gokkun, Possible School Setting

I don't have a sample image, only going off by pure memory.

I'm looking for a manga/doujin where the protag is caught in situations where he's getting sucked off by girls so that they can drink his cum. Afaik, it seems to be in a world where this is normal behavior but it might be possible they were hypnotized. I do remember that there is a scene where a girl sucks him off right after doing sports. There also seems to be a point the protag comments that the girls seem to ignore him despite them sucking him off just minutes earlier.

My recollection of this is that it's by shiwasu no okina, but had no luck finding it so I could be badly mistaken.

Thanks in advance for any input!