noun
gentle but firm; soft on the outside, hard on the inside
Describes a person who appears gentle and approachable but has a strong, unwavering inner character. Often used as a compliment for someone who is kind yet resolute.
彼は外柔内剛な人で、普段は優しいが、いざという時はとても頼りになる。
He is a gentle but firm person—usually kind, but very dependable when it counts.
I approached the negotiation with a spirit of being gentle but firm.