"Merfolk Race's Advanced Technology"
Those who had awakened abilities and those with superior bloodlines could naturally transform into humanoid form to live outside of the sea, but those who didn't have such a blessing would always be bound to live in the sea.
Fortunately, with the changes in technology and the efforts of the Merfolk race, the sea was rarely polluted, allowing the Merfolk race to occupy the sea so easily.
The cities and countries underwater were also not as old-fashioned as in stories with western-style castles and such with primitive marine lives as the decorations or daily applicants of the underwater countries.
Nowadays, there were sci-fi like cities underwater, there were ruins, there were western palaces, and there were even oriental Eastern styles in various underwater cities.
After the excitement of transforming into mermaids and mermen, even the mermaid woman couldn't hold back and shared a little bit of story about her Merfolk race.