獅し子し身しん中ちゅうの虫むし

expression, noun

snake in one's bosom; treacherous friend

Idiomatic expression for a person who betrays the group they belong to, like a parasite or enemy within. Often used in political, organizational, or literary contexts.

• 彼かれはまさに獅し子し身しん中ちゅうの虫むしで、内ない部ぶから組そ織しきを壊こわそうとしていた。

  He was truly a snake in the bosom, trying to destroy the organization from within.

• 獅し子し身しん中ちゅうの虫むしという言こと葉ばは、身み内うちの裏うら切ぎり者ものを指さす。

  The phrase 'a worm in the lion's body' refers to a traitor within one's own circle.