under the rose

idiomatic

(idiomatic) In secret; secretly, privately.

Japanese Meaning

秘密裏に（密かに）行われる様子を表す表現 / 内密な、秘匿された状態を示す表現

The executives signed the contract under the rose to keep the acquisition confidential.

幹部たちは買収を内密に進めるため、契約に密かに署名した。

Sense（1）

(idiomatic) In secret; secretly, privately.