Polycoria is the medical term for having multiple pupils in a single eye. It's commonly called "double pupils," or "pupula duplex," since it's normally only two pupils.
In Japanese, the common term for polycoria is choudou 重瞳, literally "stacked pupils," and the technical term is is ta-doukou-shou 多瞳孔症, "multiple pupil condition."
In anime, characters with natural double pupils are almost nonexistent. Honestly, I only know one example, and a pretty well-known one, too:
Anime: Shinsekai Yori 新世界より (Episode 18)