Wow, excellent work on this game! I've just been playing this with my daughter and I actually had an emotional experience whilst playing. I think Miiri Can't Sleep has real potential :D
If I may, I'd just like to mention 2 small minor things as feedback, which will hopefully be useful to you:
1. On the main menu, I was reading the story, clicking through to the next bit of text and I continued clicking completely missing the Start button on the cloud below, lol :D If you could maybe just make the cloud background a little brighter so the purple text for "Start" stands out more, that would be amazing :)
2. I found using the Z and WASD keys to remove a line quite challenging for my clumsy fingers, lol :p What would be nice is maybe using Ctrl and WASD to remove the line instead? I think it would make the undoing action much easier as the Ctrl key feels much easier to access whilst using the WASD keys :) but that's just my personal opinion of course :)
Overall I think you've done an amazing job with this game. I love the music, the visuals, the storyline and you've absolutely hit the mark with the theme. Once again, well done on your project, you should be very proud :D