At first, I thought the idea of an RPG where you kill yourself was kind of dumb. Then I levelled up, and realised that it got harder to grind as I got more HP. That was neat.
Given how unintuitive trying to kill yourself is, I think you should add a delay between your action and the enemy's. Because they happen simultaneously, it looks like you're hitting them, and it takes a while to notice that you're damaging yourself.
I liked the art style. Kind of reminds me of Realm of the Mad God.