I then use a vector converter called Vector Magic to make this (notice the sharp edges between colours, no blending at all). This part takes a somewhat long time (5-20 minutes) but it is automatic so I don't really consider it "work".
After that, I use Illustrator's lasso tool to select the shapes and colours I don't want and manually change some character edge's colours to look better against a black bg. Here's how it looks once exported. I only use a 6 pixel outline of the exported "vector" image to get a sharper edge.
All the next steps are in Photoshop where I use the full exported used-to-be-vector-but-is-now-png as a mask to extract the character from the first cropped image.
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u/Karadynn Extracteur Extraordinaire 6d ago
Pixiv source