内ない剛ごう

noun

tough at heart; strong-willed inside

Describes a person who appears gentle or soft on the outside but is resolute and strong on the inside. Often used in contrast to 外柔 (がいじゅう, outwardly gentle).

• 彼かれは内ない剛ごうの人ひとで、見みかけによらず芯しんが強つよい。

  He is tough at heart, and despite his appearance, he has a strong core.

• 外がい柔じゅう内ない剛ごうという言こと葉ばがある。

  There is a saying: 'gentle on the outside, tough on the inside.'