A man with plans to propose to his girlfriend hides an engagement ring in the ancient underwater ruins off Japan's Yonaguni Island. When he goes missing she must investigate and remember what happened. A man with plans to propose to his girlfriend hides an engagement ring in the ancient underwater ruins off Japan's Yonaguni Island. When he goes missing she must investigate and remember what happened. A man with plans to propose to his girlfriend hides an engagement ring in the ancient underwater ruins off Japan's Yonaguni Island. When he goes missing she must investigate and remember what happened. A man with plans to propose to his girlfriend hides an engagement ring in the ancient underwater ruins off Japan's Yonaguni Island. When he goes missing she must investigate and remember what happened.