open up SAI and make a new canvas. use a small size, ranging from 1 - 400px. use the binary brush at 1 px and sketch guidelines.

set that layer to a low opacity and create a new layer. draw your sketch here using the same size binary tool.

set THAT layer to a low opacity and combine with guidelines layer. create new layer above both and carefully draw your lineart.

cleanup time! delete the combined guidelines + sketch layer. create new layer and put a bg so you can see colors + transparency.

under the lineart but above the bg, make a new layer. this is your coloring layer. for this, i used my bucket tool set to 'all image' and 'color difference'. fill in the lineart.

on that same layer, pick a darker but somewhat similar color to shade with for all the colors. make sure it's still noticeable! add in your mid shades.

now pick a third darker color that's darker than the colors that you have! not too dark though, just dark enough to see the difference. add shade w/ dithering.

added in extra details, such as Maizono's hairclips, blush, and lines on her clothing.

best part! go to the lineart layer. set that bad boy to 'preserve opacity'. use some of the colors that you used on the sprite and color the lienart! go wild with it!