Sixth-graders Kosuke and Natsume grew up in the same apartment building as childhood friends. During summer break, while playing in the apartment building that is set to be demolished, they find themselves caught in a strange phenomenon. All they can see around them is a vast sea. Will Kosuke and the others make it back to their world? A journey of farewells in summer has just begun.
Because it is populated by TOP 10 ranking since 2020, it is still a work in progress. Multiple links in the same country lead to different streaming versions.