In manga and anime, "circle eyes," maru-me ○目, are eyes drawn as white circles with black outlines, typically used when a character is overwhelmed, shocked, startled, or scared, but sometimes just a simple way to draw eyes when they're being silly.
Effectively, they're a simplified type of "white eyes," shirome 白目.
It's also spelled maru-me 丸目, and also called zero-me ○目, because they look like zeroes.
- Hair strands sticking out also symbolize being overwhelmed.
Note that eyes drawn as fully black circles, that is, as dots, are called "dot eyes," ten-me 点目, instead.
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