I’ve read this a loong time ago, so i might me mistaken about some details.

The story is about a high school student (uke) that lost a bet (i think), thus had to confess to the teacher (seme) though not having any kind of romantic feelings for him.
I think that in the begging the teacher didn’t buy it, but found messing with the uke a fun thing to do (messing but not in a sexual way).

One thing i know for sure is that, by the end, another guy (student) shows up, having feelings for the teacher and the uke, already in love, felt desparate to know if the seme liked him back.
The teacher had to make a choice, and for that, i think they were in a school trip, he had to enter the room of the one he had chosen.
Before the scheduled time of the choice, the uke saw the teacher entering the other guy’s room. Assuming he had been rejected he decided to just go home.

Because we are talking about a manga, of course all of that was a misunderstanding: the teacher intended to first reject that guy and then enter the uke’s room.

Don’t remember how they get together but they surely do.

And that’s it. I’ve been looking for this manga for like 5 years but never got to found it. So, please, if anyone knows its name and would tell me, i’d be extremely happy!