Using Coin Lockers
Coin lockers (コインロッカー) are found in most Japanese train stations apart from very small stations, and at many major department stores and tourist attractions and allow you to ditch your bag for a reasonable fee.
Paying for a locker with an Apple Wallet Suica card.
Benefits of Coin Lockers
By using coin lockers I've managed to stop off for day trips on my way between two other destinations, or when staying at a capsule hotel for a quick stop off I find it best to leave my large luggage at the station as space is usually so limited.
If you arrive at your destination early and can't check into your hotel for a few hours, they can be a handy alternative to bringing your bags straight to the hotel so you can explore.
Next time you're travelling between two destinations, try stop off somewhere interesting on the way for a few hours and use a locker to store your bags as you explore. I've visited many places this way such as Kurashiki, a day trip to Kyoto, and even left my bags in a port lockers to visit islands in the Seto Inland Sea.
Finding Coin Lockers
Usually the lockers are near the ticket gates and well signposted , though in large Shinkansen stations you may find them all over. Sometimes when the lockers are spread out there are information screens telling you where to go to find vacant lockers. There's usually different sized lockers available, increasing in cost with size.
Coin Lockers at the base of Sapporo TV Tower.
How to Use Coin Lockers
Despite the name Coin Locker, these days usually only small rural stations will have lockers that take coins. It's now more common to use your IC Card on a touch screen to pay for the locker, and often the card then acts as your key too so you just touch it again to unlock and collect your bag. It's also possible sometimes to pay by contactless bank card and you receive a QR Code receipt for unlocking.
Rates and Maximum Stay
For 24 hour lockers, rates are calculated from midnight to midnight, so after midnight on the first day you will be charged for one full day. Always check the maximum stay allowed if you are planning to use lockers overnight.
Small stations with lockers that use actual coins may be 24 hours max.
Large train stations usually allow up to 3 days.
Airports may allow longer, up to a week.
Long Term Storage is usually available at larger train stations at a separate desk, or you can use a service like TA-Q-BIN.
There's plenty of other ways to travel light in Japan - I’ve written more tips here!