The manga is interesting because it has some lore behind it, even if confusing, hell If we try to stretch it a bit, the MC is clearly oblivious that he is still actively walking the path of a BL character while trying to be a Mob, more precisely the "side-character" trope, even if he refuses to.
-All his acquaintances are Gay, including his Brother ("Whole Family being Gay" trope).
-He has had many people interested in him ("popular side-character" trope).
-He has triggered the "in "X" years" flag ("We made a promise" trope).
-He actively avoids guys despite not being homophobic (""homophobic but no" friend/classmate" trope).
-The fact he is a mob character. (I have seen a couple of BL mangas that don't reveal the name of the Mob characters till the end and even make a extra of them getting together for comedy sake because the readers take a small liking to them)
Our MC is literally that one character in BL mangas that doesn't get his story unless either the readers love him, all main couples get their story done, or the author wants him to have his own story.
Which fits perfectly in the universe lore, as the MC keeps avoiding his fate by creating more and more Main Couples, the Readers love the MC and just want to know his fate either way he goes (some routing for his successes, others routing for his demise, while others are set on him changing his mind on his own and ending whit the guy he set his first and only flag whit (Im on that side)), and the Author is literally the force that is pushing the MC into all the Flag situations, basically the BL god that controls that universe, its actually genius if this was the intention of the author, of it being like a battle between a BL writer and a Character of his world that refuses to abide by his wishes of giving him a story.
Sorry for the wall of text