Kaoru Maniac

Akihito's can hide nothing from his lover, Kaoru. That's because Kaoru's nose can decode anything, with the slightest smell he knows what you ate for breakfast yesterday and where, who you've met with, or if anything is wrong with your body. Akihito met with some guy that day, and Kaoru smelling something weird with him, forbade Akihito ever to see the guy again. Why would Kaoru do such thing?