Hello there.
Please think about people using a non-qwerty keyboard for the inputs, to be mapped on the actual letter, not on the key position.
I'm using an AZERTY keyboard, so I got every "A" wrong as they got considered as "Q". Also, please translate the menu, I don't speak japanese, so I have no idea if they are difficulty level or what's the purpose of going on higher difficulty.
If it's a difficulty level, some different reward could be interesting, here the 3 level give the same topless animation.
And please make a music that's not 3s looping.
Else there is a potential in the game, a story mode could even be made.