If there is harem story where MC is pursued by girls, but at the ending chooses his male best friend/teammate over girls? Nothing as explicit as smut, of course. Edit: Yuri harem into maleXFem!MC is also alright, since this seemed hard to find.
At first glance that seems like a good premise for an hilarious one-shot, but on closer inspection it is really fucked up. I mean the whole indecisive protagonist leading on a bunch of girls is already kind of detestable. You can kind of forgive it because the protagonist is usually too dense to know what he's doing, and the girls are fully aware of what they're getting into. Your scenario though has the protagonist leading these poor girls on, knowing they're all going to fail. Seriously what the fuck man, what sort of cruel sadist gets off playing with peoples emotions like that?
Watch all of it. Spoiler It has what you want and BIG TWIST at the end What if ... (scenario) Manga (One Shot) https://myanimelist.net/manga/91159/Harem_Manga_no_Shujinkou_daga_Gay_nano_de_Mainichi_ga_Tsurai Manga (dubious) https://myanimelist.net/manga/975/Ludwig_Kakumei
This is almost, kind of what you want https://www.novelupdates.com/series/is-it-tough-being-a-friend/