Series: A place to return to (hagaitai)

A clam and shell marisa lives in a yukkuarium being bullied by a chen and youmu for their inferior skills in the land. They dream of returning to their habitat, the sea, where the tables will turn and they will be the ones thriving as "the ruler of the seas"

One day mister relents and releases them to the wild, placing them on the beach as they requested. Yeah, let's just say they didn't really thrive as they thought they would.