noun
child's mind; childlike innocence; naivete
Refers to the pure, innocent, and straightforward way of thinking characteristic of a child. Often used in expressions like 童心に返る (return to one's childlike innocence) or 童心を忘れない (not forget one's childlike heart).
大人になっても童心を忘れたくない。
Even as an adult, I don't want to lose my childlike innocence.
彼は童心に返
He returned to his childlike mind and played innocently.