I'm a long time DDR player (foot level 12) and this threw me for a loop instantly with it's left/right brain gameplay, like learning to ride a bike backwards or trying to type on a different keyboard layout. Couldn't even get past stage 3 once the music interchanging all the different alternating notes in different colours.
Although stylistically cute, I think it would serve the player better to have the arrows/keys written on the mochi rather than having the faces because it forces my brain to translate the mochi's colour into the corresponding orientation and then having to translate that to the finger I must use. I think because of how brains work I keep flipping the arrow on one side to the opposite side of my other hand.
Otherwise its a really well put together game! But I fear my mind will tear in two if I keep going at it :)