So, yeah. Pretty much what it's written above: Do you know any manga in which one (or more) character is religious, or something similar and he's gay, but obviously he cannot say anything because no one will ever understand and they'll only make fun of him or treat him badly? Just, I don't know, anything that talks about religious topics. I don't need gay priests or something like that, just one or more characters who are gay and want to have a gay relationship but they can't because of *things*.

I don't know if it makes sense. But, please, I've been searching something like this for about weeks and I found nothing. So, if you could help me, I would be very happy. Thanks and please?

Maiden Rose, possibly. He wants to have a relationship but struggles internally with it due to public expectations of him. It's been a while since I read it, but I think he is a religious figure...? Or practically one at least. Though, I can't remember if the expectations are for him to be heterosexual or to be celibate...

Maybe-but-probably-not, Giglio by the same mangaka; "gay priest in denial" sort of story. It's probably more dramatic and less introspective than you'd want.

Can't think of anything else. Good luck with your searching!

Oh, thank you!
I've already read Giglio, and it was really good! It was not the type I was searching, though.
I'll try Maiden Rose, now! I'll let you know what I think of it. ^^ Thank you, thank you ~

It's not really fair to call this yaoi, but there's a chance you'd really end up liking IS - Otoko Demo Onna Demo Nai Sei.

It isn't really the sort of story I like, but I think Koisuru Boukun is a sort of classic yaoi about homophobia (not specifically religious, though if I remember right).

Also Haikei, Niisan-sama is really awesome and definitely fits "want to have a gay relationship but they can't because of *things*", though be forewarned the *thing* is incest.

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MW, though it's really a lot more complicated than that, being seinen and written by Osamu Tezuka. Also, it's not yaoi in the sense that it's porn, because it's not, but it does feature a male/male sexual relationship involving a very religious character.