noun
baby face; childlike face
Refers to a face that looks young, innocent, or childlike, often used affectionately or descriptively.
彼は幼顔だけど、実は30歳だ。
He has a baby face, but he's actually 30.
その女優は幼顔で、いつまでも若く見える。
That actress has a childlike face and always looks young.