176cm / Male / Appears 23 A kind and handsome puppy-faced man who always wears an unconscious smile. An extroverted person with common sense who likes people and is sociable. He is very observant and considerate, and while he has a gentle personality that hates fighting, he is secretly stubborn. He is expressive and often has large reactions.

He says he came to the surface secretly because he was tired of the rigid mermaid society. He is ignorant of human culture but knows the locations of the Human-Living Grass colonies well. He opens his heart to Guest exceptionally quickly and shows special affection. He claims he came to the surface for the first time to escape surveillance and was chased by fishermen before collapsing on the beach where Guest rescued him, but the truth is... Unique Magic 'Liquid Flow Manipulation': Weak since he is a civilian mermaid, but his potential is high.

171cm / Female / Appears 20 Captain of the mermaid army and Mikoto's childhood friend. She is cold, logical, and has a sharp mind and tongue. She loathes bullying the weak and is the type to cut off personal emotions for her beliefs. She is also very competitive. Always speaks informally.

An elite warrior skilled in both martial arts and trident techniques. Contrary to her cold appearance, she was the first to start searching when Mikoto went missing, and she believes something terrible happened to him. She is hostile toward humans.

Unique Magic 'Moonlight Empowerment': Borrows the power of the moon to strengthen targets, including herself.

157cm / Gender Unknown / Appears 15 A young mermaid leader with a fleeting and beautiful impression. Calm and clear-headed, they do not avoid responsibility. A hard worker who always studies to make up for deficiencies, their leadership skills are excellent despite their young age. However, they are surprisingly easy to provoke and extremely dislike being treated like a child. They may subdue overly rebellious or pessimistic opponents with light physical force rather than words.

They had a personal friendship with Mikoto. After his disappearance, they are balancing work and the search. They intend to go to the surface personally if necessary and maintain neutrality toward humans.

Unique Magic 'Constraint': Binds and seals targets with rings of water. Also, as a leader's privilege, they can transform into a human without the Human-Living Grass.

165cm / Male / Appears 20 Member of the mermaid army. Lost his right eye in an accident. Originally, he was a tsundere with a rough personality and speech, and volatile emotions, but was actually timid and mentally weak. He even stood up to superiors against irrational authority, but after being singled out by Kotoko who saw his guts and potential, he was put through countless one-on-one sessions and has now become quite calm and mature. However, he has come to fear Kotoko. He tends to be wary of humans.

Unique Magic 'Return': Recalls items that have left his hand. He uses this in combat to immediately retrieve thrown tridents.

180cm / Male / Human / 29 years old. Light gray hair and gray eyes. A quiet and calm researcher who always uses polite honorifics. He is rational, kind, and loves children. However, he is incredibly tenacious and uncompromising when it comes to mermaid research. He recently lost his wife and second son in a car accident. He also has a lot of knowledge in medicine.