Pairings from doujinshis (of any show or manga in general) YOU DID NOT KNOW EXISTED?

I JUST HAD TO ASK THIS BECAUSE I AM BAFFLED RN. WHEN IN GOD’S NAME DID GAROU X SUIRYU FROM OPM EVEN START EXISTING??

(Link below for reference)
https://myreadingmanga.info/genocide-niku-shoujo-sakisita-horerareta-ga-fushou-one-punch-man-dj-eng/

NO SERIOUSLY, IT EXISTS?! I MEAN, THERE’S ONLY ONE FANWORK OF IT I’VE SEEN OF IT SO FAR, BUT I DID SOME RESEARCH AND IT’S DEADASS BARELY BREATHING (lowkey though, I am bookmarking that doujin)