(just) between you and me
(US also (just) between us)
used to tell someone that what you are about to say should be kept secret
用来告诉某人你将要说的话要保密；作为你我之间的秘密，不要告诉别人
A: Do you think Mia is a good worker?
你认为米娅是个好员工吗?
B: Between you and me, I don't think she'll stay in this job very long.
不要告诉别人，我觉得她做这个工作不会太久。