Goood game, very fun Katana play. And the Audio is very smooth. But everything is too ...purple.
The UI could use some tweaking. The health indicator needs to be much bigger and contrasting. Right now it kinds of blends in so it doesn't feel deserved when you die. In the same department, adding a screenshake or some other indicator that to being hurt could help.
As some weapons are bigger than some of the enemies, the threat detection is compromised by weapons lying all around. This could be solved by giving weapons different shape of indicator than the enemies have. Something that could differentiate weapons from enemies at the first glance or even by peripheral vision itself.