Renge, an intense young woman obsessed with dating sims, declares herself the Host Club’s new manager! Her first order of business: give each of the Hosts a "dark side."

St. Lobelia Girl's Academy's Benio Amakusa, head of the Zuka Club, chances upon Haruhi and, instantly recognizing that she is a girl, tries to convince her to join her school and her club. Convinced that Haruhi will leave them, the boys dress up as girls to show Haruhi that she "can have big brothers AND big sisters - all in one!" Haruhi reveals that she came to Ouran for a reason, and says that she was never planning to leave for Lobelia in the first place.

Interested in the unknown ways of a "commoner's lifestyle", the Host Club makes an unannounced appearance at Haruhi's house to meet her family and see how she lives. Tamaki realizes how independent Haruhi is and some of the reasons why.

Tamaki enlists the help of Renge in teaching Nekozawa to become the princely figure his little sister is convinced he is and help him face his fear of light, eventually leading to him saving his sister from a large, unfriendly cat, leading her to be convinced of his bravery despite the wig and cloak that he wears.

Honey gets his first cavity, and the number one rule until the cavity is fixed is no sweets. He then takes his frustration out on Mori, who is being strict on Honey, but Honey realizes that Mori was punishing himself for not telling Honey to brush his teeth twice.

Haruhi's dream about the day of her admission into Ouran High School becomes a trippy Alice in Wonderland-esque fantasy. Her friends try to tell Haruhi something important, but she only realizes it when in court. At the end of the dream, she meets her mom, who tells her to "enjoy a dream like student life." She wakes up with tears in her eyes, and sees the club dressed up in costumes that look like the ones they wore in her dream.

The ailing Newspaper Club wants to obtain an interview with the popular Host Club in order to save it from being disbanded due to the lack of public interest. Or so it seems. The newspaper club tell lies in their papers, so the club leader wants to interview the host club because he thinks that Tamaki is using his parents' power to control the popular students, and wants to tell the whole school that. Apparently he thinks of Tamaki as his mortal enemy.

During summer vacation, Haruhi gets a part-time job in a pension at Karuizawa. She feels guilty at first for not saying anything to the rest of the Host Club, until they drop in unannounced. A contest erupts when they realize there is only one remaining room at the pension. Hikaru and Kaoru win by using their brotherly love act. When Haruhi's middle school friend visits, things take a turn for the worst.

Hikaru gets jealous of Haruhi's former classmate while at the pension. Kaoru pretends to be sick for the date, and instead sets up a date for Hikaru and Haruhi to try to get Hikaru to think of other people which Tamaki does not take too well. During their date, Hikaru runs off somewhere, and a thunderstorm occurs. Worried about Haruhi, Tamaki calls Hikaru, and tells him that Haruhi is afraid of thunder, letting everyone know Haruhi's weakness. In the end, Hikaru apologizes to Haruhi, who is hiding under a table in a church, during the thunderstorm and comforts her while she is crying. He apologizes for the way he acted, but Haruhi thinks he is Kaoru.

Kyoya, half-asleep, is dragged into a commoner's department store by Tamaki and the rest of the boys, who aim to study the life of ordinary people, and therefore understand more about Haruhi - or play. Kyoya ends up meeting Haruhi there, alone, and they find it interesting how each other views their lives. Towards the end, Tamaki makes a call for a "lost child", who turns out to be Kyoya, which makes Kyoya even angrier at Tamaki than he already is.

Honey has a younger brother Yasuchika, but he has a huge grudge against his sibling. It turns out the reason for his brother's grudge is that Honey eats too many cakes, causing Yasuchika to freak out.

The girls from St. Lobelia's Zuka Club finally manage to rope Haruhi into their academy, and it is up to the Host Club boys and Ranka to save her from Benio Amakusa stealing her first kiss - until Kyouya reminds them of Haruhi's real first kiss in a previous episode. The episode ends with the Lobelia's Zuka Club chasing Haruhi around the stage, attempting to steal her second kiss.

A prequel that tells the story of how the twins were convinced to help form the club, including the "Which One is Hikaru?" game that they always played, including their past with the maid who led them to believe that no one would ever be able to tell them apart, and the cruel trick that they played on a girl in middle school.

Haruhi's class has a Halloween event - The Halloween Special Fear Trial Tournament- in which groups do their best to scare the living daylights out of each other! The class rep isn't so keen on this idea, though, and enlists Haruhi to help him. Kaoru, meanwhile, contemplates a sad truth. Nekozawa decides to scare the group of Haruhi, Kaoru, Hikaru, and the class rep.

When the son of a gangster, Ritsu Kasanoda, seeks Mori for tips on how to change his scary image and gain friends, the Host Club immediately jumps at the opportunity to change his image, making many humorous results of their efforts. The members of the Host Club also frequently call him Casanova and bossa nova. However, Ritsu ends up discovering Haruhi's secret.

After Ritsu walks in on Haruhi changing, he later joins the Host Club, but as a customer. When he insists on Haruhi as his host, the other hosts get nervous and the clients get excited. Tamaki starts to realize his feelings for Haruhi, and Ritsu nearly goes insane, while Haruhi remains blissfully oblivious.

Kyoya recalls when he first meets Tamaki two years ago, and how he only became friends with him due to Tamaki being the heir to the Suou family businesses. He initially put up with Tamaki's odd requests, traveling all over Japan, but eventually snapped. From that point on, however, Kyoya could be his real self in front of Tamaki and they became true friends.

The Host Club participates in the annual school festival. Tamaki's father and grandmother turn up there. However, the arrival of Eclair Tonnerre, a woman who Tamaki was told to take care of by his grandmother, brings an unforeseen turn of events. Haruhi also learns of Tamaki's history, and his entrance into the Suoh family.

The Host Club must race against time to keep Tamaki in Japan and save the club from disbanding. However there are a few bumps along the way, as well as a wild horse ride, fighting with Ootori family police and Grand Tonnerre taking over lots of businesses. After Hikaru gets hurt, Haruhi rides the carriage and runs after Tamaki. Haruhi convinces Tamaki to return to the Host Club and reaches for his hand, but Tamaki is stopped by Eclair Tonnerre. Haruhi falls from the carriage and off a bridge. Eclair lets go of Tamaki's arm and Tamaki thanks her before jumping from the car to save Haruhi. In the end, Haruhi, dances with all the members of the Host Club.