Translation guide
A hidden advantage or resource kept secret until needed.
To express that someone has a secret plan, skill, or resource that will give them an advantage when revealed.
Literally 'trump card'. This is the most direct and common equivalent for 'ace up one's sleeve', referring to a decisive hidden resource or strategy.
He still has an ace up his sleeve.
Literally 'hidden hand/technique'. Implies a secret move or last resort, often used in competitive contexts like sports or games.
Literally 'hidden ball/piece'. Used for a secret weapon or surprise element, often in sports, business, or entertainment.
He played his ace up his sleeve at the end of the negotiation.
He was waiting for the right moment to use his ace up his sleeve.
新製品が我が社の隠し玉だ。
The new product is our ace up our sleeve.