Hidden under the waves

One day on the ship deck, Chuuya looked down. A oddly fast humanoid figure was visible through the waves. Thinking it was a person, Chuuya stopped the ship, only to see a brown haired male, his pale skin transitioning into shiny, blue scales.

In this AU mermaids can change to humans whenever they want, unless if their gills are covered. they also can be on land without water.

top Chuuya+ sailor Chuuya
bottom Dazai+ mermaid Dazai