Your transitions from dark to light look unnatural and somewhat forced as if you quickly did them.
Also i dont see enough darks in your pictures. Always remember to use the darkest darks and lightest lights.
Also you have alot of really sharp bold contours that distract your viewers. In some places you can smoothe them out with texture/shading to make it look more natural. (not all contours i understand how anime and all works.)
I dont care if anime doesn't do this stuff or if contours are highly important. These are bare essentials in art and should be done in any work, even sketches.