I really like the art style. This time around after playing with a few different browsers and I found one where the frame rate didn't tank as soon as the game started, so I was very happy to be able to walk around this beautiful work.
One thing I think that would improve the gameplay is to add a bit of knock back to enemies when they are hit or to give the player a few invincibility frames when they are attacking to give the player a bit of space if they successfully hit the enemy. This would also help with the player keeping a bit more health as the enemies are bit bullet spongy and I couldn't really tell how much health they had or how many times I needed to hit them.
I has 0 hearts and was still able to carry on. I also got the following error when I died and hit 'R' to restart:
abort() at jsStackTrace@https://v6p9d9t4.ssl.hwcdn.net/html/8371313/InuGaidenWeb/Build/InuGaiden.framewo...
stackTrace@https://v6p9d9t4.ssl.hwcdn.net/html/8371313/InuGaidenWeb/Build/InuGaiden.framewo...
abort@https://v6p9d9t4.ssl.hwcdn.net/html/8371313/InuGaidenWeb/Build/InuGaiden.framewo...
___cxa_allocate_exception@https://v6p9d9t4.ssl.hwcdn.net/html/8371313/InuGaidenWeb/Build/InuGaiden.framewo...