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From kouhei nakajima:
1. StoryYou know the story of Taro Urashima.He got a turtle out of trouble, and went to the castle of Ryugu.But he got old due to the treasure box...So that's the end of the story? No, there is more to it.2. How to playTap the turtle icon to collect the treasure box.Return to the main screen, then by tapping the treasure box icon, and you get the experience points.As you get the experience points , the story progresses.3. Rules3 experience points are gained with one treasure box session.By tapping the experience x2 icon(top of the page), it will increase by 6.The experience x2 time is only for 2 minutes, and can be activated again an hour later.