"Please become my mate!!"...

This is the love story about an average salaryman and a merman.

Togawa is an ordinary salaryman whose days are spent simply going back and forth between his home and office. His one and only form of enjoyment are his side trips to the neighbourhood lake. He doesn't do much there. He just enjoys watching light reflect off its surface.

Then one day, Togawa went into the lake to help a child get the ball they accidentally dropped in there. However, Togawa can't swim and he was about to drown when a beautiful boy saved him. But the boy didn't have any legs... That's right, the beautiful boy is a merman and his name is Ryuka!

Togawa found himself gradually getting attracted to Ryuka... But when Ryuka said, "Let's exchange vows"...