“Coin lockers” are widespread in Japan, and are a great convenience for travellers, providing a secure place to keep your stuff.
They can be found at airports, all main rail stations, but also at suburban stations and the Tokyo metro.
They exist in several different sizes, and you pay for a 24-hour period: a small one will be around Yen 300 for the day, a mid-size one (eg. for a small rucksack) around Yen 400, and a large one (eg. for a suitcase) around Yen 500. You can usually pay using an IC card ( Pasmo or Suica card) as well as with coins.
Note that there are not so many of the largest size lockers – an available large one may be a bit more difficult to find.
The illustration shows the coin lockers at Mitaka station, a suburban station to the west of Tokyo, where you get off if you are going to the Ghibli Museum.