Painting skin
① First, dark skin colored shadows are added with the [Pen] tool → [G-Pen], and blurred with a transparent colored [Airbrush] tool → [Soft].
② After that, a pale skin color is painted with [Soft] to add volume.
At this point, while it doesn’t add to the volume, you can simulate girlish skin by painting the tips of the fingers and joints.
③ More reds are added to other parts like cheeks, eyelids, and lips.
④ Further volume is added by overlaying a new layer and adding pale purple to the darker shadows, as seen in the bangs below.
As the colors dull when too much purple is added, I only add a touch.
 Coloring the whites of the eyes and touching up
Parts-wise they would be part of the eyes, but the whites of the eyes are painted at this point.
① The base color is painted white, and shadows are added with a desaturated purple.
After that, the same color as the line art is added to the parts that touch the eyelids to simulate depth.
② To make the skin more lush, highlights are added to the cheeks and lips.
And with that, the skin is finished.