Yes, I've seen one, and read it, but I forgot where I found it....Σ(  ̄□ ̄||)
Alright~
I don't want to call you a liar, since you probably confused a different manga and thought it was about the side couple. But I am 100% sure that Beriko hasn't created any manga that featured those two as a main couple. So far there's only been extra's that has featured these characters. And non of them were of them dating, just the older guy acting all flirty. The most recent extra is in japanese, and it was about two pages long. And they appeared in a bar together, are they dating, don't know? Maybe, i cant read japanese. But i do hope that someday in a future they will have their own story. So i am waiting for that :3
You're probably right, but there's still hope..!
google this :
ぷちぷち - BL Gazette
not a manga but a yonkoma.
Is therr a spin with the the other the bully and the other guy senseis friend