瞳
ひとみ · hitomi · JLPT N2 · noun
pupil
👁️ 目 (eye) + 童 (child): the eye's little child, the dark dot at its center
The kanji pairs 目 (eye) with 童 (child, young person). The reading ひとみ is a native Japanese word, so learn it separately from the on-reading どう used in other compounds.