is a Japanese manga series written by . The manga was serialized in Square Enix's manga magazine Monthly Gangan Wing from 2002 to 2008 and in Monthly Gangan Joker in 2010. In 2004, a drama CD based on the series was released by Frontier Works. The series tells a story of a young mermaid who saves a young boy named Nagasumi Michisio from drowning. To avoid death, Nagasumi chooses the option to marry her.
A 26-episode anime television series adaptation animated by Gonzo, directed by Seiji Kishi, and written by Makoto Uezu aired in Japan on TV Tokyo between April and September 2007. Two original video animation episodes were released in November 2008 and January 2009. Odex, a Singaporean distributor, released it in English in Singapore as Seto No Hana Yome.
Plot The series revolves around a young teenage boy named Nagasumi Michishio. One day during his summer vacation at the Seto Inland Sea, Nagasumi is saved from drowning by a mermaid named Sun Seto. Under mermaid law however, either the mermaid whose identity was revealed or the human who saw the mermaid must be executed. In an attempt to save both Nagasumi and Sun's lives, Sun's family (which is the head of a mermaid Yakuza group) reluctantly decides that the two are to be married. Sun's father Gōzaburō is enraged about his daughter's sudden marriage. Between Gōzaburō's constant attempts on his life and the madcap antics of a slew of antagonists, Nagasumi has a hard time transitioning into his new married lifestyle.
Characters Michishio family
Nagasumi stands out as the most sensible member of his family, aside from his grandmother. Though usually timid, he exhibits surprising strength in dire situations, entering a heightened state—triggered by his ahoge—that allows him to evade nearly any threat. He chooses to marry Sun despite fierce opposition from most of the Seto group, except Ren and Masa. Over time, his initial sense of duty blossoms into genuine love, which he openly declares. Sun's Song of Heroes enhances his abilities in battle, though he can also tap into this power when she is endangered. After Sun saves him from drowning a second time, he proposes, and they share their first kiss.
Nagasumi's father often finds himself heartbroken due to his wife's shifting affections. She frequently dotes on Masa, leaving her husband visibly dejected—such as when she prepares a meal exclusively for Masa, leaving him to eat a lonely burger before being scolded by his boss. On another occasion, he sulks at the table after missing dinner, having been too absorbed in his gloom to notice the food. His despair peaks when his wife temporarily falls for Nagasumi, who had unwittingly taken a love potion that made him resemble Masa. Left abandoned, Nagasumi's father sits alone on a playground swing, utterly despondent.
Nagasumi's mother is cheerful and easygoing, though her fondness for Masa often irritates her husband. While her romantic interest in him has waned over time, she remains deeply devoted to her family, including her spouse. She embraces Sun and Lunar as if they were her own daughters, delighting in their presence and treating them with warmth and affection. Her nurturing nature extends to all those close to her, making their home lively and welcoming despite the occasional marital friction.
Nagasumi's paternal grandmother resides near the Seto Inland Sea. She briefly appears early in the story, hosting Nagasumi and his family during their visit. Though she does not feature prominently afterward, the family reunites with her once more by the story's conclusion.
Seto family
Sun is a mermaid and daughter of yakuza leader Gōzaburō Seto. Guided by a strong sense of honor (which she connects to the linguistic similarity between and ), she takes her role as Nagasumi's wife seriously while genuinely loving him. As a juvenile mermaid, her legs transform back into a tail when wet. She occasionally enters a dramatic "chivalry mode" accompanied by cherry blossoms and enka music. Though usually peaceful, she demonstrates skilled swordsmanship when necessary. Unlike Lunar, Sun employs bodyguards only during conflicts with Lunar's guards. Like most mermaids, she fears cats but can overcome this phobia when needed.
Gōzaburō is a sea dragon and boss of the Seto Group. Though a doting father to Sun, he despises Nagasumi for "stealing" her away. Using his influence, he and his subordinates infiltrate Nagasumi's school as staff, with Gōzaburō becoming their homeroom teacher to monitor Sun. Despite being a powerful yakuza leader with an intimidating presence, he suffers from two crippling fears: cats (stemming from a childhood trauma) and his wife, who punishes him without hesitation. His imposing demeanor often contrasts comically with these vulnerabilities, particularly when confronted by felines or his spouse's wrath.
Ren is Sun's mother and a mermaid who supports her daughter's relationship with Nagasumi. As the most feared member of the Seto Group, she maintains discipline among members, including her husband, through harsh punishments. She joins Nagasumi's school as the nurse and enjoys teasing him. Like Sun, she has a "chivalry mode" accompanied by pink petals and her version of "Namida Ichirin" (). Despite her kind appearance, she displays typical yakuza behavior when needed. Her name means lotus flower, reflecting her elegant but formidable nature.
Seto Group members
Masa is a Seto Group member and Sun's kendo instructor, recognizable by his sunglasses. After performing CPR on Nagasumi (humorously framed as stealing his first kiss), he becomes Nagasumi's math teacher, using yakuza-themed word problems. Though typically silent, he becomes talkative when drunk. He supports Nagasumi and Sun's relationship, unlike most Seto members. Later revealed as Akeno Shiranui's long-lost brother, he regains memories of his past position (which Akeno inherited) and reconciles with her. Unlike most merfolk, he overcame his fear of cats as a child. His protective nature emerges when defending Akeno from threats.
Known as "Spiral Shell" ("conch shell" in the anime), is a petite Seto Group assassin and Sun's loyal companion. She attacks by firing high-velocity water bullets from an endless supply of shells. Opposed to Sun's relationship with Nagasumi—whom she derisively calls "sea louse"—she frequently distracts Sun to ambush him while advocating for a Nagasumi-Lunar pairing. Like most merfolk, she suffers from ailurophobia, though the family cat inexplicably favors her, much to her annoyance. Her small stature belies her deadly accuracy with her signature shell-based weaponry.
Shark Fujishiro, a Seto Group member, first attacks Nagasumi during the Michishio family's visit to the Seto home. Having served the clan since Sun's childhood, he later becomes Nagasumi's P.E. teacher. He consistently attempts to eat Nagasumi, believing this would solve all problems and allow everyone to return home. This logic extends to other disruptive individuals, whether they're admirers of Sun/Lunar or even fellow gang members. While often seen sleeping, his unique ability allows him to transform just his head into a shark form. He speaks with a characteristic questioning inflection, regardless of context.
(Maguro) (Burio) (Ajitaro) Maguro, Burio, and Ajitaro are bumbling triplets who serve as Gozaburo's elite guards in the Seto Group. Despite their rank, their cowardice and dimwittedness often force others to take command. They debut when summoned to eliminate Nagasumi and a cat, but immediately panic upon seeing the feline. Enrolled as students at Nagasumi's school, they retain fish-like facial features in human form, initially unsettling classmates who eventually grow accustomed to them. The brothers are distinguished by their accessories: Maguro wears a black student cap (sometimes), Burio goes bareheaded, and Ajitaro sports small rounded sunglasses.
Nakajima, a Seto Group member, is actually a giant octopus who joins Nagasumi's school as a teacher. Unlike other members, he never appears in human form and remains visibly octopus-shaped, often stuck in the school due to his massive size. Several of his tentacles appear to be missing. His presence creates darkly humorous moments, particularly when the school cafeteria serves octopus dishes to students while he remains trapped nearby.
Edomae family
Lunar, Sun's childhood friend and rival, is a popular idol singer who uses her mermaid voice. Driven by competitiveness, she initially tries to steal Nagasumi from Sun by making him her servant after he sees her true form. She moves into his home and gradually develops genuine feelings, even attempting to marry him in the manga (with Sun's eventual acceptance). Lunar commands a personal army of Isono Junior High boys, constantly clashing with Sun's guards. She speaks in the plural form and announces herself with a distinctive "hohoho" laugh. Like most mermaids, she fears cats despite her regal demeanor.
President Edomae leads the construction-oriented Edomae Group as Lunar's imposing father. Clad in a black skintight suit, this silent figure parodies the Terminator, complete with metallic body sounds and iconic film references like a thumbs-up "I'll be back" delivery. Though intimidating, he demonstrates quiet devotion to Lunar, supporting her relationship with Nagasumi more openly than Gozaburo does with Sun. His extreme wealth funds extravagant gestures like a $10 billion film project. In a recurring gag, he infiltrates Nagasumi's school disguised as a female student to monitor Lunar, ultimately revealing unexpected laser eye capabilities. His character theme parodies the Terminator 2: Judgment Day score.
Lunar's mother, formerly known as Edomae before her divorce, was believed to have abandoned her family when Lunar was five. In reality, she served a ten-year prison sentence for intentionally running over her neglectful husband with a car. She shares Lunar's dramatic personality traits, recognizing their similarity when entering her passionate "mode". Her influence shaped Lunar's development - the childhood "war songs" she taught fostered Lunar's competitive spirit with Sun, while her absence indirectly motivated Lunar's idol career (partly hoping her father would see her on television). Her criminal past and flamboyant temperament create an unconventional but understanding bond with her daughter.
Other characters
Mawari, Nagasumi's childhood friend and police chief's daughter, harbors a crush on him while sternly policing his behavior. Aspiring to become a police chief like her father, her peacekeeping efforts are accompanied by a symbolic whistle sound. Her name references Zenigata Heiji and the Japanese term "Omawari-san" (police officer). As leader of Isono Junior High's Public Morals Committee, she commands the school's largest faction, rivaling both Sun and Lunar's groups. Though perceptive enough to nearly uncover Sun's mermaid identity, Nagasumi consistently intervenes. She frequently delivers her signature line: .
Hideyoshi Sarutobi, nicknamed "Saru" (meaning monkey), is Nagasumi's perverted friend whose name references Sarutobi Sasuke and Toyotomi Hideyoshi. Initially befriending Kai Mikawa for money, he genuinely grows to care for him, becoming his loyal protector - often appearing suddenly like his ninja namesake. He periodically adopts a bearded sage persona ("Saru Roshi"), parodying Dragon Balls Master Roshi to dispense lewd advice. This "Pervy Hermit" alter ego reinforces his comedic role while maintaining his monkey-like characteristics, creating a humorous contrast with his occasional moments of genuine loyalty and friendship.