It's a very cool game!
However, a bug occurred at the end of the true ending route that made it impossible to progress!
There is a cliff on the right side of the boss battle, but if you take damage there and fall down, you will have to survive in a place that cannot be seen on the screen, and you will not be able to receive or deal damage.
I found out that I could restart by pressing the 0 key, and was able to clear the game after that!
It was a really great game and great music!