Pretty Kickass
Reminds me of Straw Hat Samurai (using the mouse for sword strikes), but I definitely appreciate the use of WASD to move. Overall, this is a really good game, with awesome art design, upgrades, and a still relatively unused mouse-driven-attack style.
I do have a couple complaints though. First, when you start engaging in more intense fights, the camera moves around too much, often setting off unintentional dash attacks. With such a precise attacking system, you need to be aware of how the camera will affect things. Second, the game is too short. Yes, the upgrades add replay value, but overall, the game takes 15-20 minutes to beat, and I'm not sure I'd play it over and over just to get more powerful moves. You have an intriguing story, so build on it to allow for a longer game.
Otherwise, this is a damn good standalone game, and I look forward to seeing how you build on it in the future.