child's mind; young heart; innocent mind
Refers to the naive, pure, or undeveloped way of thinking and feeling characteristic of a child. Often used in contexts of innocence, simplicity, or childishness.
幼心にも、その光景は美しいと感じた。
Even to my child's mind, that scene felt beautiful.
彼のいたずらには、どこか幼心を感じさせるものがある。
His pranks have something that reminds one of a child's heart.