I'm gonna go with Narcolepsy. It's a disorder characterized by sudden, uncontrolled lapses into deep, but brief sleep.
It's useful in some situations. However, there are some problems. For example, if you're going to be in some kind of freak accident, you wouldn't notice it because you're sleeping. And that is bad.
It would be nice if there's a new character in KS with this disorder. The ending scene will be hilarious.
Hisao: Hey, new girl.
New girl: Huh?
Hisao: I think that I'm falling in love with you.
New girl: Zzzzzzzz...
....WTF?
