Aquadine — after his mother was hospitalized due to an unknown illness, Robin Liun works part-time as a gondolier to make ends meet, but under the pseudonym Ciel. One evening, when he finishes his tours, a mysterious voice beckons him to discover a beautiful mermaid. She dives underwater shortly after their meeting, leading him to believe that Ancient Aquadin was real. His city was named after the sea deity Levios. Robin continues to live his double life, making new friends and learning more about the Merfolk civilization.