After a pretty mermaid named Sun (who happens to be the daughter of a merman yakuza) saves him from drowning, Nagasumi has to make a choice: marry Sun or sleep with the fishes!
Nagasumi escorts Sun to a festival so they can get better acquainted before their big day. They better skip the small talk - if Sun's dad has his way, Nagasumi won't live long enough to ask for a second date!
Nagasumi has to tell Sun that it's time for him to return home. While he tries to find the right moment, Sun's tiny bodyguard, Maki the Conch, looks for her own perfect moment - to assassinate Nagasumi!
Sun and Nagasumi leave Maki behind and venture out to take in the sights and sounds of the city. When Nagasumi has to confront a couple of bullies, they may wish the tiny terror was still around!
Newly enrolled Sun makes quite a splash among her classmates on the first day of school, but Nagasumi is more concerned with some of the new teachers - Sun's dad and his goons!
Mawari thinks there's something fishy about Sun, so she begins an investigation. When the clues lead to a dangerous situation, Sun might have to reveal her secret to keep her new friends safe!
When Nagasumi discovers the secret mermaid identity of a famous pop star named Luna, the little diva demands he become her personal slave! Her plans for childhood rival Sun are even more drastic.
To prevent Luna's fans and Sun's followers from murdering each other, Nagasumi offers himself as the grand prize in an all-out singing competition between the two girls!
A young merman name Kai challenges Nagasumi for Sun's affection! Only one of her suitors will claim the mermaid's hand in this contest of field games and guided missiles!
Nobody believes Nagasumi when he claims he's being stalked by a relentless force of destruction, a huge man with a shotgun who won't stop until his prey is cornered - and terminated!
Luna requests some one-on-one tutoring from Nagasumi, but no amount of studying can prepare him for the consequences when he's caught in a compromising position with his pop idol pupil!
Luna and Nagasumi's wedding is interrupted by the dramatic entrance of an uninvited guest - and instead of bringing a gift to the ceremony, this party crasher is brandishing a blade!
With her glasses broken and vision blurry, the Class President tells a helpful boy about her crush on a friend. Of course, she'll soon realize this helpful boy is the same boy she likes - Nagasumi!
Akeno's job is to snoop around and send mermaids who don't fit in on land back to the sea. It doesn't take much to fail her tests, and now Sun's happiness is at risk!!
Akeno isn't just causing problems with mermaids; the entire school is in chaos thanks to her growing reputation as a troublemaker. Mawari might be the only one who can bring peace back to the halls.
During a class outing to Kyoto, Akeno tries teaching Sun how to control the bodily changes that happen when she gets wet. As they close the bathroom door behind them, Mawari totally gets the wrong idea!
When the whole class gulps down a special potion meant to bring out the deepest desires of mortals, Akeno's secret plot to drive Sun away from Nagasumi is derailed!
Luna and Sun's dads can't seem to unlock the mysteries of the teenage heart. To understand what their little girls are feeling, the two tough guys decide to put themselves into their daughters' shoes - and skirts!
After receiving a love letter, Nagasumi learns that a little attention goes a long way. A mermaid potion makes girls crazy about him - and turns every guy around him into a murderous psychopath!
Luna needs a scene partner to portray her lover, and Sun goes to ridiculous lengths to play the manly role. When Luna decides to work on a ventriloquist routine for a talent show, Maki is on hand to assist.
Akeno suspects Masa knew her missing brother in the past, but he doesn't remember life before the Seto gang. When he learns just how correct Akeno's hunch really is, Nagasumi must go all out to protect Masa!
Rumors spread that Kai is deathly ill, and when the whole gang goes out of their way to make his "last days" extra special, he begins to believe it himself!
Nagasumi's feeling some emotional turmoil after his first spat with Sun, but when he learns her whole family could be in grave danger, he and his friends jump into action!
The Seto clan is locked in battle with Yoshio's forces! If Nagasumi and Sun are to live happily ever after, he'll have to be braver than he's ever been!
