Masochist
Ryu found this fourth floor to be more amazing than he could have ever imagined. Here, not only did his body not feel any fatigue, he didn't become injured either, not in any true sense. The only real exchange he had to make was with his Focus Qi. The longer he fought, the more his mind seemed drained. But, the Fourth Floor also seemed to have the ability to more quickly replenish Focus Qi as well, as far as Ryu could tell, sleeping here for an half hour was the equivalent of eight in the real world.
Ryu wasn't at the point yet where he could go without sleep entirely, but as a Qi Refinement expert, staying up for several days wasn't much of a problem. And, when he did need to sleep, about four to five hours was more than enough.