Digitalis

If you just watch out for the half-twist in the very late section, the rest drops to D20 level as long as you can handle the drills. If you've cleared a D20 and have confidence in your stamina, I think you can break on this right away.

20

Even at level 20, this is bottom tier; there are tons of level 19s that are harder to full combo than this.

Personally, I think it's around level 19.

One of the easiest charts among the 21s; if you're good at twists, it's easy.