Where can I leave my luggage for the day?

Short answer

Two separate systems: coin lockers you work yourself, and staffed counters that will hold a bag for up to two weeks.

Coin lockers at a Japanese railway station

Two systems, not one

Coin lockers are the self-service option. At Narita they sit in all three terminals across several floors, all of them before security, in small, medium and large — plus an extra-large at Terminal 3 that takes long items like skis.

Staffed baggage storage is the other one, run at counters by delivery companies. Haneda's holds a bag for up to two weeks, to a limit of 30kg and 300cm for the three sides added together. Narita's counters charge across three size bands and rates differ by company, so the price is a question for the desk rather than something you can look up in advance.

The midnight rule that catches people

Narita's daily-charge lockers do not count in 24-hour blocks. A day ends at midnight. Put a bag in at 9pm, take it out at 1am, and you are charged for two days — the airport gives exactly that example.

Other locations run an hourly system instead: one price for the first six hours, then a further charge every 24 hours. Either way continuous use caps at eight days, or five for the extra-large lockers.

Paying, and where to look

Every locker inside Narita is a touch-panel unit and takes Suica, so "coin locker" is a name rather than a constraint. You do not need to hunt for change first.

Both airports keep storage counters on the public side of security, on the arrival and departure floors. At Narita, counters carrying the government's hands-free travel mark are certified to handle foreign visitors in English — worth steering towards if you have anything to ask about your bag.