Saw this drawing (Figure 1) in the Animal Crossing. Then remembered I saw similar makeup in a Japanese musical (Figure 2).

It looks like the black marker/makeup at the corners of the mouth is to show the personality of a character. In case this, it means this character is evil/vile.

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https://artsandculture.google.com/asset/%E4%B8%89%E4%BB%A3%E7%9B%AE%E5%A4%A7%E8%B0%B7%E9%AC%BC%E6%AC%A1%E3%81%AE%E5%A5%B4%E6%B1%9F%E6%88%B8%E5%85%B5%E8%A1%9B-kabuki-actor-%C5%8Ctani-oniji-iii-as-yakko-edobei-in-the-play-the-colored-reins-of-a-loving-wife-koi-ny%C5%8Db%C5%8D-somewake-tazuna/4QHN10FjxTa2Fg?hl=zh-CN