It is a shounen-ai manga where the main character is social and outgoing. The other guy seems to be the strait-laced worker who is generally poker faced. They some how come together and the main character discovers that the other guy is actually just socially awkward having grown up very sheltered. He does not have friends, never drank alcohol, etc. Main character ends up liking the other guy.

soredemo kamawanai?

if there is an option between "to do" and "not to do", I will always choose the latter.

"what kind of crazy, twisted conclusion is that...?" - banana bread no puding

Also sounds like Sayonara, Itoshi no My Friend - This isn't Shounen-Ai but nothing "happens" until Vol. 2.

Edit The more I think about it, this may not be it... the guy drinks alcohol, he just has a very low tolerance...

@Nyajinsky Yes! Thank you!
@Xanity Haha I love that one too! Thanks!