Onime no Kyo did not like to sleep.
There were the obvious reasons of course; it gave enemies a (slim) opportunity to wound him (killing would be giving them too much credit). It was also a waste of time. Hours spent sleeping could be better spent traveling, drinking, killing, or just fighting in general. Sleep was dull. Now he was traveling in a much larger group than normal and he had even more reasons not to sleep.
He was the best fighter in their little band (well, anywhere, but especially in their group) if he was alert then everyone else could sleep. Where as if he slept, everyone else had to keep watch in groups of two. If his servants were tired, then they couldn't do their jobs as well.
Not only that, but who knows what crap one of his servants might get themselves into if he didn't watch them. Dog-Face was especially bad at staying out of his way and out of danger. Who would pay for everything if she died? And Yukimura needed to be watched, just a bit. One could never tell what he was up to. But all of these reasons were not the main reason that Demon Eyes Kyo did not like to sleep.
He didn't always know if he would wake up the next morning.
This body was not his own. He was reminded of that every time he moved. It was clumsier than he was used to. To everyone else it may seem normal, but he wasn't used to it. This wasn't his body, it was Kyoshiro's -that asshole. His soul was always hovering in the background. Watching.
It pissed him off.
Kyoshiro had taken over in the forest. Kyo would not repeat that experience for anything. It was not like before when he hadn't been fully 'awake'. Instead of being asleep, the feeling was one of being crammed into a cage. One that was shrinking. Rapidly. Kyoshiro didn't have to worry about that. It was his body. He had a nice little soul-room. Bastard.
Sleeping was just another way of letting down his guard. He might fall asleep in camp, and wake up in a cage too small to hold him. If the cage grew too small when he was inside…
Onime no Kyo knew about death. You cannot deal out over one thousand death sentences without knowing something about it. But when you're soul is compressed until you're non-existent? What then?
He didn't like questions that he couldn't answer, avoid, or slice in half. He didn't like being in a body that wasn't his and wouldn't move as fast or as powerfully as he was used to. He didn't like having to go through a maze of Mibu Clan underlings before he got what was rightfully his and took his revenge on Kyoshiro once and for all. All of these problems were brought to the forefront of his mind at night, when there was nothing and no one to distract him. He might avoid these thoughts if he slept, but there was one problem in that.
Onime no Kyo did not like to sleep.