I have read it too, but I think it was a side story of something else. Can't remember either
Now I'm having doubts but I'm pretty sure it wasn't a side story because it was right at the start/they were introduced as the main characters since I remember clearly that at the start even if there was a side couple initially it was just them.
At best if it's a side story it's more likely that the two came from another comic and the creator did a comic about them, but I clearly remember the story started with them and there was no other couple around/they weren't the side couple in the comic.
Maybe later on they did get an additional side couple but they were the main one, that's for sure.
Because the story started with them and focused on them.
Found it, it's Mr. Beta
I've been trying to find this anywhere and everywhere but no matter what, be it reddit or any other site, no one seems to know this?
It's either me having gone crazy or I don't know what.
Either way, it was a fully colored, probably Korean BL where the two are teachers.
One is a Beta with dark/black hair and the other a Alpha with light/white hair, taller than the Beta.
There was a Omega student who got in heat and it caused the Alpha to react to it and to suppress it he injected himself with suppressants but used a lot and it still didn't work.
The Beta teacher worried about it offers to help, explaining he learned that mimicking the marking process will slowly make him feel better and that since he's a Beta he doesn't need to worry about actually pairing.
I just can't find it no matter what and I did try to look in all the tagged ones but even if the tag says Alpha x Beta it still add Alpha x Omegas and mostly Japanese Manga making the research too time consuming.