on the sly (on za surai)

Idiom Secrets

意味

secretly; in a sneaky way

秘密で; 狡猾な方法で (himitsu de; kōkatsu na hōhō de)

例文

"He met her on the sly without telling anyone."

"彼は誰にも言わずに秘密で彼女に会った。" (Kare wa dare ni mo iwazu ni **himitsu de** kanojo ni atta.)