Ao no Flag. It isn't about a gay guy but it includes a depiction of a "normal" gay dude.
I'm gonna assume you don't want a feminine kind of gay guy, or someone who likes to have sex a lot.
heard these were recommend by the lgbt community
http://www.mangago.me/read-manga/otouto_no_otto/
http://www.mangago.me/read-manga/ganbare_nakamura_kun/
http://www.mangago.me/read-manga/shimanami_tasogare/
based on real life apparently
http://www.mangago.me/read-manga/tatoeba_konna_koi_no_hanashi/
romance ain't the focus
http://www.mangago.me/read-manga/my_son_is_probably_gay/
two gay dudes instead of straight boi turned gay
http://www.mangago.me/read-manga/dark_heaven/
^no seme or uke, one of them had sex a lot but not because he's a sex crazed maniac but because he's obligated to do so under a contract he signed for the music industry
http://www.mangago.me/read-manga/cinema_next_door/
^ no sex at all, actually they never really talked about their sexuality. they just got together naturally imo.
no femininity, there is a straight guy tho
http://www.mangago.me/read-manga/soredemo_yasashii_koi_o_suru/
http://www.mangago.me/read-manga/reply/
Stfu shinks

I’ve always like anime and manga, but you don’t see a lot of if any unambiguously gay male characters who aren’t hyper feminine sex criminals. As for yaoi, I mean no disrespect to the genre, but it’s equally unrealistic, albeit for different reasons. So if anyone could suggest some titles about ‘normal’ gay dudes, I’d really appreciate it.