After his mother's death, high school student Kosaku Sakamoto travels to Tokyo to live with a friend of his mother's, Ibari Ozora. Kosaku meets Ibari and his four daughters: Tsugumi, Tsubame, Hibari and Suzume.
When Ibari sees what he thinks is Hibari and Kosaku sleeping together, he has a heart attack. After recovering, he decides to use a "Spartan method", having the trainer "Tatsu the Spartan" teach Hibari to be more manly.
Hibari sings in a rock band at school and wins first place in the contest. A few of the girls, led by Kaori Hanazono, are jealous of Hibari. The next day, Kaori is lead to believe that Hibari could be male and plans to expose her.
Kosaku, after having a nightmare about Hibari, plans to become manlier to repel Hibari's "perversions" and visits the school's boxing club. He becomes a club member and falls in love with Rie, the club manager, making Hibari jealous.
The boxing club depart for their training camp at Umineko Inn, with Kosaku and Shiina in one room while Hibari and Rie share another. The four of them have fallen into a love square.
Tsugumi has recently fallen in love with a boy named Bunta Umiushi. Unfortunately Ibari does not approve as her boyfriend, as the Umiushi family are the Ozora family's traditional enemies.
A young man tries to flirt with Hibari, annoying her. Later, he arrives at the house. He is the son of Tatsu the Spartan who lost a fight against Hibari. He wishes to fight Hibari for revenge, without knowing she is the girl from before.
Kaji invites Tsubame on a date then leaves before she can say no. Tsubame asks Hibari to pretend to be her on the date and reject Kaji for her. Kosaku and Tsubame monitor the date to hear how it goes and guide Hibari.
Suzume invites her friends over for a study session, one of whom she has a crush on. After arriving, Katagiri, Suzume's crush, instantly falls in love with Hibari instead of her.
Kosaku's friend/rival, Daisuke Itagaki is coming over to visit him. They have a long-running competition to see who can get a girlfriend first. Hibari offers to help Kosaku win by pretending to be his girlfriend, and he reluctantly agrees.
When bikini shopping, Hibari humiliates Kaori after she stole her bikini, collapsing the changing room walls and exposing Kaori's breasts in public. For revenge, Kaori plans to strip Hibari naked at the beach.
Kosaku and Hibari go to summer camp. Kaori suggests to the girls that they have a test of courage and invites the boys to participate, though she rigs the partner selections to make sure Hibari is separated from Kosaku.
Ibari is hosting the annual gambling tournament for every yakuza boss in Japan, with Hibari as the Game Master. Yakkun, the idiot son of the boss of the Crazy Group, falls in love with Hibari and insists on marrying her.
Feeling he should spend time away from Hibari, Kosaku temporarily moves out of the Ozora house, moving into Kaji's house. Meanwhile, Honda, a popular boy and known womanizer, intends to make Hibari his 1000th conquest.
Seiji receives his first love letter but is worried his job as a yakuza would make him an unsuitable husband. The girl turns out to be Hanako, Kaori's friend who developed a crush on Seiji after seeing him at the beach.
Tsugumi has a new boyfriend, Takakura Yujiro, a young actor hoping to become a movie star. Yujiro becomes the lead actor in a movie, but his movie contract says he is not allowed to get married as long as he is a movie star.
Kosaku finds an old album containing pictures of his mother. Ibari reveals Kosaku's mother, Harue, was once his girlfriend. Hibari becomes upset that Ibari has a whole album of Harue but only one picture of her mother and runs away.
Ever since he failed to seduce Hibari, Honda has become afraid of girls. After he sees Hibari flirting with Kosaku he decides to try seduce Hibari again and spreads a rumour that Kosaku and Hibari were making out.
Don Corleone, a Mafia Don and old friend of Ibari's, visits the Ozora house. Corleone wants his son Michael to marry one of Ibari's daughters and threatens to have Ibari assassinated if he refuses. Michael chooses Hibari.
Amachi, the PE coach is in love with homeroom teacher Iwasaki. Iwasaki announces she will be doing home visits, starting with the Ozora house. Ibari decides to turn the house from a Yakuza stronghold into a respectable family home.
Hibari is offered to compete in the Women's Wrestling Tournament. Kosaku realises one of the wrestlers is Rie, former manager of his boxing club. He offers to help Rie train, then Hibari decides to join the tournament as well.
All the girls at school have a crush on popular girl Otori Jun, the Volleyball Captain. After seeing how skilled she is, Otori asks Hibari to join the team but she refuses. Otori then develops a crush on her.
The Ozora family have money troubles and many of their soldiers are quitting to find real jobs. Ibari refuses to change his business until he finds a piece of Suzume's homework proving she would prefer him to be an honest businessman.
The Kurikara Detective Agency is asked to come to Monkey Island to solve a terrifying mystery. On the plane journey a passenger is presumably murdered, until discovered that someone is playing a practical joke.
Kosaku and the Ozora's end up stranded on a desert island and meet a tribe. The chief's daughter, Ribahi, is identical to Hibari and Kosaku develops a crush on her, making Hibari jealous.
Each year, the Ozora's and the Umiushi's fight over who owns the Kotobuki Shrine. To settle this, the two bosses are ordered by the Zenigame group's boss to settle this with a baseball game.
Ibari falls in love with Fumiko, a coffee shop manager. He contemplates marrying her, attempting to get over the death of his former wife, whilst also keeping his occupation a secret.
The park is invaded by child delinquents called the Kid Gangsters. Suzume decides to form a Good Kids Gang to defeat the Kid Gangsters, despite one of the gangsters having a crush on her.
After a girl develops a crush on Kosaku, she hires a private detective to investigate his relationship with Hibari. The detective discovers that she was assigned male at birth, fuelling the girl to swear to defeat Hibari.
Ibari plans a party for Suzume's birthday, being on Christmas Eve. Kosaku invites Rie, whilst Shiina invites himself over so he can seduce Hibari. This upsets Rie and causes Kosaku to take action.
Kosaku dreams of himself as a Heian era Lord and Hibari a Geisha. An ogre appears so Amachi has the entire city gather to hunt it. The ogre, named Oni, hides in the Ozora house and befriends them.
While Kosaku and Hibari were dreaming their souls left their bodies and accidentally returned to the wrong ones, leaving them trapped in each other's bodies.
After seeing Kaji's desperation to be with Tsubame, Hibari and Kosaku try to convince her to date him for a few days, despite her lack of interest in him.
The White Alligators are finally able to possess Hibari, granting her psychic powers, including time travel. She uses this to travel to the next day of school.
