This is a good start. The core mechanics work well. The gameplay is simple and easy to understand, but still challenging to play. The upgrades are good, and there was always something useful. The UI was clear. I used mouse and keyboard.
I started with the default character, and liked the shuirken. After beating the level I moved on to level 2 and tried the second character. I really did not like the straight in front attack of the katana, especially with the eye enemies that swarmed at the start of that level. I did a lot of running as I worked out how to use it and survive. I see that it is powerful, but I much prefer it as a secondary or tertiary weapon, over the starting one. It is great for the boss fights, but even there I prefer to have the other weapons to deal with the swarms and the katana for hitting the boss. I went back to the default character after that level. I liked the scythes, especially when you get 2 or more spinning around you. I largely ran around enemies in circles, letting the attacks do their thing, and collecting what was left behind. I'd move out as a new wave came in and then corral them all into a new circle. I played through the third level and got several shop upgrades. I never had enough to unlock another character, so mostly spent on the top section of upgrades.
The difficulty rose at a good rate. The bosses hit hard, but were also pretty easy to avoid. The harder versions of existing enemies that showed up with the boss fights was a nice touch.
The description for level 3 says to reach level 10 to awaken its guardian, but I was only at level 7 when the timer hit 5 minutes and the boss appeared.
This was a nice submission and fun to play.