The character art has its charm, although I feel it is a little unpolished. I am not a fan of the japanese voices, but that is down to personal preference. That said, I did like how they were used just before the next level started. Was a nice touch
The gameplay was good, but I feel it needs better level design, specially with the enemy generators pumping out too many enemies in the early levels before you can get upgrades. Besides that, the small issues with the physics and animations made the game less enjoyable that it should have been
Overall I think there is a lot of potential here. With plenty of polish this can become a very unique platformer, particularly if you make the most of the digging mechanic