Omega has been wound up a lot.

Why does Omega clockwork have black marks on the skin?

Because sweating will bring out metal wear, there will be black things printed on the skin.

It's just that I sweated a lot when I wore it in summer, and the bracelet was soaked with sweat. When the bracelet moves, it will take out the worn metal, which will naturally be black on the skin, so the words are rough and impartial.