Sleep

Sleep is said to be vital for mortals and is also said that those that don't get enough sleep tend to be cranky, crazy even.

But, those symptoms are merely of the beginning phases, since the symptoms branch out into a dangerous territory by each passing day.

The same is true for those on Miorus.

The only difference would the fact that the gap between the days they need sleep widens as they grow, inching nearer to their higher limits. Similar to us, they too needed 8 hours of sleep, but since they could actually store the energy they recovered in their sleeps, the gap in between their needs to sleep widens constantly.

Yet,

Ken had become someone who couldn't fulfil his need to rest even if he wanted to, since his senses were something honed at the front lines of the battlefields....

He was the kind to remain alert at all times, as it had become something akin to an habit and an instinct to him.