In between the sea and the land

Since long ago, human civilization had lived on the ocean floor. However, there were many humans who wanted to live above the surface and they moved to land creating a fundamental separation between the two.
After her school closes down, 18-year old high school student, Hana blue, from the sea village, Shioshishio, has to go to Midorijima, platinum jail, on the surface. What follows is her struggles to adjust to a new environment and the relationships between the sea and land people, and her new thoughts about the new game named 'rhyme'.

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