Really funny concept! Really like the idea of a fish flopping around trying not to get hit. My only criticism is that I found it really hard to tell whether I'm about to be hit or not - 9/10 times it feels like the blade just goes through me? Maybe shadows on the blades would help.
I feel like if this is properly polished with some really wacky physics (and more japanese flavor) it could be a really funny time killer.