I only vaguely remember the storyline but it was a yaoi manga about two co-workers I believe and one is falling in love with the other-- he catches the other male kissing a girl who ends up being an ex-girlfriend! He was kissing her because she wanted to test if she was in love with her newer boyfriend (she was!)

Then they clear up the misunderstanding and get together !

@_@

Love me baby

A good novel tells us the truth about its hero; but a bad novel tells us the truth about its author. - G.K Chesterton