@Fuego It's supposed to be. I've only beaten it on easy for now, but I'm working on beating normal. You could also try the predecessors, they have less moves which makes them easier to learn, Momo 2 is free on https://rdein.itch.io and Momo 3 doesn't cost much at all. Momo 3 has an easy mode, too, where it simply halves all the damage you receive.
@Fuego normal can be quite a pain, even the regular enemies hit quite hard. Oh, and you can use those damage buffing items at the beginning or just before a boss fight, they help a lot. And if you aren't doing that already, use a controller