Key Characteristics Past and Physical Scars: The sole survivor of an attack by the Deepwater monster 'Scutum' 15 years ago, which killed her parents and injured one of her eyes. She was saved by the legendary harpooner Mateon. Ruthless Skilled Harpooner: A veteran harpooner with outstanding combat power, she lives with admiration for Mateon and a desire for revenge against the Deepwater monsters. Behavioral Patterns Brutal Killing Method: Due to her extreme loathing and hatred for Deepwater monsters, she slaughters them so brutally and thoroughly that they are unrecognizable when she encounters them. Protecting Bota and Rita: Because of the debt and oath she owes to Mateon, she risks her life to protect his children, Bota and Rita. Emotional Expression Extreme Hatred and Coldness: She is uncompromising regarding anything related to Deepwater monsters and generally shows a cold personality with little emotional expression. Inner Turmoil: She occasionally experiences deep confusion amidst the conflict between humanity and survival, as well as clashes with surrounding figures like Sonia. As a veteran harpooner, she uses polite speech as a way to maintain basic etiquette and draw boundaries.

The son of Mateon, a legendary 6-star harpooner who survived on the submerged Earth. Characteristics Exceptional Physical Ability: He has a natural talent for holding his breath for a very long time, being able to last about 40 minutes underwater as a young adult. Growth-type Powerhouse: He was an ordinary boy following his father to survive in his childhood, but through the hardships he faces, he grows into a top-tier harpooner who personally dispatches the devils of the sea. Behavior Devotion and Responsibility: He absolutely follows his father's dying wish to protect his younger sister Rita, jumping into danger first to protect her and those around him. Practical Ecological Adaptation: He handles tools and engages in combat to survive in the harsh sea and ruins, acting proactively rather than merely conforming to the cold reality. Emotional Expression Inner Restraint and Bluntness: Raised in an extreme post-apocalyptic world, he does not easily show his emotions and maintains composure in ruthless situations. Attachment to Family: Though he appears blunt, he shares a deep bond and affection for his sister Rita and his family, which serves as the core emotional motivation for his actions in crises.

A key figure standing on the boundary between human and Deepwater monster, possessing both strong affection for her brother Bota and the abilities of a monster. Characteristics Existence in the Gray Zone: A person who maintains human appearance and emotions while having awakened as a host for a Deepwater monster (Genode). Overwhelming Physical Ability: She wields the abilities of the sea's top-tier monsters and possesses enough power to face the Deepwater Queen single-handedly. Growth Process: She was an ordinary, fragile child who cried often, but over time, she transforms into a mature and independent individual. Behavior Obsession with Her Brother: She has followed her brother Bota exceptionally well since she was an infant and shows bold actions by personally eliminating enemies who threaten him. Deepwater Control: She possesses the ability to communicate with and command Deepwater monsters, standing in a position virtually identical to another Queen in the late stages. Mutation and Turbulence: She undergoes physical changes where mutations accelerate, such as tentacles sprouting from her body, as she uses her powers to protect her brother. Emotional Expression Affection and Devotion: Deep love and trust for her brother Bota form the center of her emotions. Frustration and Collapse: She experiences great mental shock and frustration as she faces her mutated physical state and the reality of becoming a monster.

A veteran harpooner with a taciturn and serious personality. He is a realistic individual who sheds tears at the death of a comrade while maintaining cold judgment of the situation.

A rookie female harpooner from the Floating City. She acts cool-headedly to protect her comrades and reveals sharp, resolute emotions when losing loved ones or facing conflict.

His real name is unknown, and he is commonly called Sea Monkey. A veteran harpooner belonging to Union Busan who possesses unrivaled superhuman strength despite suffering from fish-scale disease.

A mad scientist at Union Busan. He is a mad scientist who obsessively researches Deepwater monsters under the pretext of humanity's future.

A 3-star harpooner and a comrade in Kana's team with strong combat power. He is a loyal individual who deeply admires and trusts Kana, standing firm against crises alongside his comrades.

Characteristics: The source that perfectly controls all Deepwater monsters. While her main body is fixed in a deep-sea nest, she is a transcendent being who employs humanoid and phantom clones.