was reminded of this one tho that thingy only happened in the side stories (afair): https://www.mangago.me/read-manga/in_the_castle_the_dragon_s_erotic_education/
Friends milk?
It could be already said but idk for sure what one you could be talking about but it might just me one of the few I found, idk for sure tho https://www.mangago.me/read-manga/male_boob_milk_pheromone/
https://www.mangago.me/read-manga/how_to_make_tasty_milk/
https://www.mangago.me/read-manga/sweet_rich_milk/
https://www.mangago.me/read-manga/friend_s_milk/
This one someone else already found but just in case
I need help finding a yaoi about a guy who's nipples produce milk