My Bride is a Mermaid

So in short, My Bride Is A Mermaid is just how it sounds. A teenage boy named Nagasumi is at the beach with his family when he suddenly finds himself to far from the shore and starts to drown. Instead what ends up happening is Sun, a mermaid, saves his life. Now in the mermaid world if your seen by a human that human must die and or the mermaid. The only way for them both to live is if Nagasumi and Sun marry, and so they plan to (eventually). Of course, first comes the courting period.