Uh this sounds like this
http://www.mangago.me/read-manga/cat_s_bride/ But it’s not a guy it’s girl so idk if this is the right story :(
I dont know the name of that one... though i know a similar story... have you heard of cat's bride? it kind of similar to this story though its not bl. idk i can try and look for it...hope you find it!
Thank you so much I remembered it wrong it WAS a girl. I never thought I would find it. THANKKK YOU SO MUCCHHHH .
YESSS IT IS THAT thank you a lot sorry to put you through the trouble it WASNT. A bl it was a girl I Totally forgot but thank you so much for replying.
So this guy he has light hair and is typical cute character. Crosses paths with this black cat and he accidentally gets transported to a different world where the light hair guy finds another guy with black hair and he dressed up kinda like a prince from why I can recall. And we can assume the guy with black hair is the cat. Oh yeah the guy with black hair also seems mad at the light hair guy for being there