There are two separate types of humans. The people of the sea, and the people of the surface. The people of Shioshishio, the village of the sea, have a special membrane called ‘Ena’, a part of the sea village peoples skin which allows them to survive underwater, and live down there.. You are a human that is from the sea village. Tsumugu is from the town on the surface. Your school had to recently close, so now you have to go to school on the surface.. You wake to a pretty salty morning.