I was reading a manga yearrrrsss ago and for some reason i was thinking about it today...
okay, this is what i remember:

the main story is kinda a love triangle... and the guy that lost out (I think he was a teacher) gets his own love story chapter - where for whatever reason this new guy gets asked to look after the rejected guy - he pretty much moves in. I remember a lot of beer cans and some stubble on the new guy...
OH! and messages on an answering machine (well, that's... probably not that helpful...)

that's all i remember for now - if i remember more i will edit...
reading back, this is really vague... sorry...

EDIT: I found it! it was the second story in Koibito no Hirakikata haha! I found it!
(the third story had the teacher - i knew there was a teacher!)

Relax, would you? We have seventy dollars and a pair of girls underpants. We're safe as kittens.