Actually, I don't remember if it was shonen ai or yaoi, but the story goes something like this:

It's set in high school. There are two male friends who are sort of popular, I think. Then, while they're having lunch? one of them notices a boy in another table looking their way and this guy thinks that that boy is looking at his friend and comes to the conclusion that that boy likes his friend, so he approaches the boy and tells him he will help him to get together with his friend. Things happen, MC starts falling for the boy, and by the end of the story, it's revealed that the boy was actually looking (and in love with) MC and not his friend. Also, (although I don't remember this well) MC's friend starts liking the boy too?

Anyway, I read it a looong time ago, it was a short story, but can't recall the name of the manga or the author or the characters' names. Would reaaally appreciate it if someone could recognize the plot and tell me what's its name.

I feel like it could be Koimonogatari (TAGURA Tohru) ?

Kanjou Spectrum also has a similar story.

Omg, it is Kanjou Spectrum!! Finally, after so long, I can read it again. Thank you so, so much!! @dalek

Also, thanks a lot to @kuroipon too! It wasn't the one I was looking for but, since it has the same plot, kind of, I'll make sure to read it, so thanks a lot for the recommendation!

Thank you both, so much!! ❤