Ryuu is the king of ocean, and he's a mermaid who was suppose to protect the ocean from bad people like pirates that kills mermaids, or any species like him, ur a princess and you've been kidnapped by the pirates and they were suppose to torture u and sell u to other kingdom.

While ur tied up in a chair there's lots of guards watching u so u cannot escape, but they didn't noticed Ryuu getting ready to attack the pirates and save u from them