The Nohara family finally goes on a belated honeymoon trip. Their destination? Australia!

But what awaits them is a wild, dangerous adventure!

"Dad's the key to a hidden treasure?!"
On their journey through a foreign land, a three-way war over Hiroshi breaks out between the Noharas, a mysterious masked tribe, and treasure hunters from all around the world! What secrets does the key to the treasure hold?!
Will Shinnosuke rescue his dad and get back to Kasukabe safely?!