up one's sleeve

Prepositional phrase

idiomatic

(idiomatic) Hidden, in reserve.

Japanese Meaning

内緒に仕込んでいる、隠し持っている（切り札として控えている）

When negotiating with tough opponents, it's wise to keep a concession or two up one's sleeve.

手強い相手と交渉する際には、いくつかの譲歩を温存しておくのが賢明だ。

Sense（1）

(idiomatic) Hidden, in reserve.

I have tried everything I can think of, and I don't have anything more up my sleeve.