Main characters are two guys shion (dark skin light hair) and rui (white skin black hair) and shion somehow becomes a girl and rui tries to fuck him
is it this one?
http://www.mangago.zone/read-manga/fucked_by_my_best_friend/
I just realized this site has no adds so they probably stealing our data but am I gonna stop coming here now?? hell no, them illegal mangas be too good
This site does have ads but if you make an account you don't see them.
do you know why that is?
The ads are shown when you read mangas without an account which are ads for affiliate sites working with mangago. One example if when you refresh a mangago chapter link, you'll be transported to one of their websites instead.
I don't know why they made the decision if that's what you're asking though.
ohh, understand now thank you