Sure! Here's an example of a simple 2D anime game where you can kill monsters using JavaScript:
Monster Slayer
In this game, you control a blue circle (representing the player) using the left and right arrow keys (or A and D keys). Your goal is to avoid colliding with the red circle (representing the monster). If you collide with the monster, a game over message will appear, and you can refresh the page to play again.
Please note that this is a very basic example. You can add more features, levels, animations, and graphics based on your requirements and game design.