na-adjective, noun
simple and honest; unsophisticated
Describes a person or character that is plain, unpretentious, and sincere, without worldly cunning. Often used positively for rustic honesty.
彼は質朴な人柄で、誰からも好かれる。
He has a simple and honest personality, and is liked by everyone.
田舎の質朴な暮らしに憧れる。
I long for the simple, unsophisticated life in the countryside.
Compound of 質 (substance, quality) and 朴 (simple, plain). The exact historical derivation is uncertain, but the combination conveys plainness of character.