Having grown up there, the place holds a lot of memories, but while playing, they suddenly get caught up in a mysterious phenomenon and when they regain consciousness, they see an entire ocean before them as the housing complex has drifted into a mysterious sea and Kosuke and Natsume with it.

One day during their summer vacation, they go to a housing complex that is scheduled to be demolished. Having grown up there, the place holds a lot of memories, but while playing, they suddenly get caught up in a mysterious phenomenon.