luggage storeage period

can I store my luggage in the locker for 3 days..

Yes you can for 3 days but only the electronic lockers. You must pay the three days at the end and if you do not collect your luggage by than the train conductors will remove the bags.
However luggage in lockers are very hard to get, especially if you have medium and bigger bags.

I recommend using another service. If you in Tokyo you could use the luggage storage service at Haneda Airport http://www.haneda-airport.jp/inter/en/premises/service/delivery.html

Hope this helps!!
Have fun!

how does the electronic lockers work.

You use a IC card like Suica or Pasmo but make sure you fill it first.
You choose a locker that is free and then put your stuff inside. Then push the door until you here a click and lights are flashing.
Select English if needed,
Then go to the IC card reader and tap your IC card. Door should lock and stop flashing, you should also get a receipt with the locker number so you know which locker it is when you pick it up. It should have also taken the locker fee for the day. Different pricing for each but for this example lets say 500yen.
Then three days later when you go pick up your luggage. Go to the machine, select English if needed, then select open locker.
Then tap your IC card (Must be the same IC card that was used) Three day fee would be taken from the card and your locker door should be unlocked.

Hope this helps!!
Have fun!!

Forgot to mention three days is actually three days...

Day 1 - Drop off luggage in locker
Day 2
Day 3 - Must pick up luggage

Hope this helps!!
Have fun!!