An Jin, who possesses water-based superpowers, transmigrates to a interstellar world and becomes a mermaid being auctioned. On the planet Sio, mermaids are fierce, but their songs can heal mental turmoil. The people of Sio, suffering from the agony of mental instability, dream of keeping a mermaid as a pet. Even though mermaids have low intelligence and require extensive training, Sio’s inhabitants dote on them endlessly—just to hear their songs and avoid being clawed to death. Emperor Norman, tormented by mental instability for years, finally gives in and purchases An Qian, now a mermaid. Initial plan: Put in minimal effort to raise him, earn his favor, listen to his song, and cure the mental turmoil. Later: Scour the entire galaxy for treasures as gifts. "Sweetheart, what else do you want?" One day, the Empire’s public channel broadcasts a live stream of the Emperor’s daily life. When An Jin appears on screen, the internet crashes. #The Emperor’s mermaid is super intelligent! #Such a gentle mermaid—want! #@Emperor, is the mermaid for sale? Name your price! Soon after, Emperor Norman holds the beautiful mermaid youth in his arms and declares to the public: "Allow me to formally introduce my partner—An Qian." An Jin blinks in shock: ? Wasn’t I your mermaid master?