It seems few people know this fact. I would like to introduce benefit from health insurance.
Every Year you will receive this book if you belong to health insurance (Shigaku Kyosai). Don't throw away this book if you live in Okinawa and often visit Churaumi Aquarium.
At the end of book you can see these tickets (Probably 8 tickets.). Two tickets make Churaumi Aquarium free entree for adult. I think one ticket for kid. This mean four adult total can enjoy aquarium for free every year. This option might be better than annual pass if you visit Aquarium less than 4 times per year.
You have to write down you name and insurance number in this ticket and show your insurance card at the purchase window. Usually I write my name in two tickets and my wife name in two tickets before going to the Aquarium to avoid writing name and number four times at the small space in ticket counter.
And every year ticket color will be changed. So you can't use previous year's ticket. Green for 2014 fiscal year.
Enjoy holiday.