He has a sad past experience and also he keeps on sniffing taeho because it's the only scent he can smell and when taeho asks him if he has a habit of smelling him you can see that ho seems stunned as he is afraid that taeho will find out and also in the earlier chapter where taeho comes home to find ho sleeping in the closet it was because ho became anxious without ho so he slipped into the closet full of taeho's scent
Ooh my god sorry for the spoiler to anyone angered but I just can't seem to shut up

It is Ho have some ability or what? Or ability to sense something? I'm confused.