It's been two years since Junichi was stood up on Christmas Eve, which has scarred his heart and made him wary of love. While buying lunch for his friends, he helps Sae, a friend of his sister, Miya, which catches the attention of the popular school idol, Haruka. Later that afternoon, he goes to the library to meet his friend Masayoshi but encounters Haruka again and helps carry her books while she teases him before leaving with her friend Hibiki. Junichi's interactions with Haruka makes him believe in love again, so one afternoon he confesses to her. Haruka rejects him but she admires his honesty.

Because of Haruka's rejection, Junichi feels dejected and unable to sleep well. He goes to the infirmary to get some rest, but he unexpectedly finds Haruka resting there too. Despite what happened, Haruka is still interested with him which lifts his spirits up. After being dragged by Haruka into the school pool the next day, Junichi brings her to the library where he later confesses to her a second time. Unsure what to say, she allows him to confess to her again as many time as he wants and kisses his eyebrow.

Ever since the kiss, the energetic Junichi has attracted the attention of the girls which makes Haruka jealous. He asks her to kiss him on the eyebrows again but instead she brings him to an abandoned water pump shed where he kisses her behind her knees like a puppy. Junichi wants to kiss her that way again and keep asking her for the next few days. After taking Hibiki’s advice on what to do with their relationship, Haruka lets Junichi spoil her including both of them engaging in some roleplay with him feeding her ramen, much to bewilderment of everyone in the cafeteria. Later that night, Haruka thinks how much fun she had with him.

Junichi decides to ask Haruka out on Christmas Eve. While asking her out, both of them realize that they have met before on Christmas Eve last year and cheered each other over their respective problems. Haruka refuses Junichi's offer, but instead invites him to her family's Christmas Eve party. On Christmas Eve, Junichi and Haruka decides to relax in the hotel swimming pool before meeting her family but when her family can't make it, she invites him to her hotel room. With the two of them alone, Haruka reveals her insecurities to Junichi as she has fallen in love with him but thinks he is no longer interested with her. Junichi hugs her and assures her he hasn’t and both of them declare their love for each other. Ten years later, Hibiki visits Haruka and Junichi, now a happily married couple.

On the night when he was stood up, a heartbroken Junichi is about to go home when he meets his friend Kaoru. To cheer him up, she invites him to her home to eat cake with her and her mother. Two years later, they remain friends who snark at each other. After punching him and bringing him to the infirmary, Kaoru asks Junichi to come to the flower garden after school. Thinking she wants to confess to him, he instead finds Kaoru with her friend Keiko, both asking advice about Keiko's crush. He suggests writing a letter to him. As the two of them go home, Junichi tells Kaoru of what he thought she was going to do at the flower garden, which leaves her flustered as she heads for her part-time job at a restaurant. As she tries to forget about the incident, Junichi arrives at the restaurant, making her nervous every time she sees him. Figuring out why she is acting strange, she in turn realizes that her feelings for him have grown.

As Kaoru is in denial about her feelings for Junichi, she gets into a fight with Keiko’s crush upon learning he made fun of the letter she wrote to him by showing it to his friends. Junichi stops her and follows her to the rooftop, where they talk about Keiko's romantic problems. Their conversation turns to their own relationship, which hasn't changed much. She plays a joke on him and accidentally kisses him which was both their first kiss. Wanting payback for what happened, Junichi brings Kaoru to the library to tickle her. Unsatisfied, he changes his mind and kisses her navel instead. As the two walk home while laughing at what they did, they help two boys retrieve their stuck birdie on a tree. As Kaoru rushes to her part-time job, Junichi realizes he's finding her cuter than ever. Later, while Kaoru is on her way to work, she sees her mother meeting with an unfamiliar man.

The next day, Kaoru doesn't come to school, worrying Junichi. Skipping the rest of the day's classes, he frantically searches for her at the places where they hang out, until he takes a clue from overhearing Hibiki and Haruka, and looks for Kaoru at her part-time job. When he confronts her, she reveals that she spent the night at a manga café after she had a fight with her mother over learning she is dating another man and thinking about remarrying. She is against it, being content with the way things are with her mother. Junichi counsels Kaoru about her problems, promising to be there for her when she needs him. She in turn admits she needs his companionship. The next day, Junichi is glad to see her at school in her usual self again, after she and her mother have talked things over.

Noticing the growing attraction between Junichi and Kaoru, Masayoshi and Keiko decide to set the two up together by making them meet at the infirmary. There, Junichi tries to ask Kaoru out on a date on Christmas Eve, but to his surprise she has already planned to go out with him. On Christmas Eve, Kaoru decides to bring Junichi to the top of the new Port Tower despite his fear of heights. As they watch the snow fall, Kaoru confesses her love to Junichi, admitting she wants them to be closer. He in turn admits he loves her as well, that he wants to be with her forever, and they kiss. When Kaoru misses the last bus home, Junichi invites Kaoru to his home to stay for the night where both of them sleep together. Ever since, Junichi and Kaoru have become a loving couple.

Junichi, still afraid to love due to a traumatic event that happened two years ago, sees a beautiful new student named Sae Nakata. He gets to know her eventually when he goes looking for her to properly thank her for finding his wallet, and his sister Miya eventually introducing him to her. That afternoon, when Junichi sees Sae being scared by a "big dog" and panics, Junichi takes her to the restaurant where Kaoru was working to calm her down. It is here that she gets enamored by Kaoru's uniform, and, saying she wants to wear one sometime, Junichi suggests to her that she takes a part-time job there. Junichi and Miya try to train her on how to become a waitress based on Kaoru's tips. With Junichi as her instructor, her training is off to a tough start, given her mistakes. Still, Sae finds a friend in the Tachibana siblings.

Sae's training to become a waitress continues with the help of Junichi and Miya, by practicing her speech skills and practicing how to change uniforms in three minutes--where Miya catches her, in a swimsuit, and Junichi in a compromising position when Sae tripped. They even have had special training in a hot spring with some doctor fish in it to further her speech skills. Sae expresses to Junichi her desire to train even harder, though he has little idea why she wants to be trained more. Her trainings did make Sae become closer to Junichi and Miya; however, one night when Sae has to sleep over at the Tachibana residence, Junichi tells her his wish that he would like to have another younger sister like her, but, to his surprise, she says doesn't want that.

Though confused as to what Sae told Junichi that night, her training goes on until the day of the job interview. She passed it, but when Junichi plans to "graduate" her, she refuses, stating that she wants to become her student forever. Junichi is happy to see Sae in her part-time job, though still confused with her. One day, Junichi accompanied Sae to the amusement park, where they rode the merry-go-round and watch a hero show. Here, Sae asks Junichi to call her by her first name, as well as asking him to be her partner for the upcoming Best Couple Contest during the school festival. Later, taking a clue from Sae's actions, Junichi holds her hand.

As Junichi decides to tell Sae how he feels for her, Sae invites him to a restaurant that serves a special parfait--one that could allegedly turn a couple into lovers by eating it. On the day of the Best Couple contest, however, Haruka and Hibiki wins first place--although Junichi and Sae, in wedding attire that she designed and sewed herself, comes in a close second. She puts the blame on herself, but Junichi says she's cuter than Haruka. Their prizes are tickets to a movie, and they get to watch it in a private room. While Junichi is in the bathroom, an English-speaking man sees through him, as to his plans for Sae, and tells him not to be afraid of failure. The man was revealed later in the pamphlet Sae was reading to be the director of the film they are about to watch. After the movie, Junichi gathered his guts to tell Sae that he likes her. This made her happy, and they became lovers from that very moment.

On the night when he was stood up, a heartbroken Junichi heads home and meets a young girl rushing home with a present for her brother. Two years later, Junichi and Masayoshi heads home where Junichi encounters the girl he met two years ago, now with a cold attitude. At school, Junichi chases after a black cat Miya talks about and meets the girl again who teases him and introduces herself as Ai Nanasaki, his sister’s classmate and member of the Swim Club. Miya later asks Junichi that night about why Ai wants to know about him, but he ignores her, causing Miya to write on his forehead while he’s asleep. The next morning, Ai helps Junichi wipe off the writings on his forehead and helps him enter the raffle Miya wanted him to enter. Despite not winning the prize Miya wanted, Junichi and Ai decide to use their prize, a 500 Yen voucher, to buy some Ōbanyaki and later pick up the trash at the beach.

Junichi, Kaoru, and Masayoshi head to the library to see the new Library committee member, but cause a ruckus there until Ai scolds them. Junichi later offers to teach Ai maths upon learning she’s taking makeup exams. While both of them are taking a break, Ai asks Junichi on what to do with her younger brother, Ikuo, since Junichi acts childish just like him. When Junichi is about to tell Ai his advice during lunch, he unintentionally offends her when he and Miya talks about Sae’s breasts. Junichi later apologizes, even humiliates himself in front of Ai and the swimming team on what he said and entering the school pool without permission. At the beach, Junichi tells Ai to spoil her brother a bit since he just wants her attention. As thanks, she gives Junichi a Inago Mask utility belt, a gift that originally was for his brother. Instead, he teaches her how to use the belt and gives it to group of young boys. That night as she goes to sleep, Ai realizes she likes Junichi.

Junichi invites Ai and Ikuo to go to the amusement park but only the former two go after Ikuo gets sick. While entering the haunted maze, Junichi starts hallucinating bizarre things around them until he snaps out of it after biting Ai’s finger. As they head to the park where they first meet, both of them ride the swing together where Ai stops it and kisses Junichi, leaving him flabbergasted. The next day, as Junichi visits Ai at the school pool to talk about yesterday, he finds Ai distraught upon learning from Hibiki that she was not selected for the upcoming swimming meet. As Ai tries to run away from them, Junichi unexpectedly chases her and dives into the pool and hugs her where she finally cries. As he consoles her on the way home, Junichi accepts Ai’s invitation to help the Swim Club’s oden food cart during the Founder’s Festival.

As Tsukasa formally opens the Founder's Festival, Junichi is helping Ai out at the Swim Club's oden food cart, where they sell out their wares, even gaining praise from the Tea Club. At the end of the festival, Ai takes Junichi to a hill with a hot spring owned by her grandfather. As the two are practically naked in the hot spring, Ai confesses her feelings for Junichi, which he also confesses his feelings for her as well, and kisses her. In the epilogue, Junichi rests on Ai's lap while watching the sunset at the same beach where they first ate Ōbanyaki together.

Two years ago, Junichi asked his childhood friend Rihoko, to come and help him select a present for his date on Christmas Eve. Rihoko, who had an unrequited love for Junichi, was sad to find out later that he was stood up. In the present, Rihoko takes a shortcut to school through a hole in a fence, but gets stuck until Junichi helps pulls her out. Realizing she is gaining weight, she seriously swears to her friend Kanae that she'll go on a diet immediately, and gives her cupcakes to Junichi. Kanae seizes this chance to invite him and Masayoshi to go ice skating with them in the weekend. However, upon visiting her seniors at the Tea Club, Rihoko unwittingly breaks her diet there eating snacks until Manaka and Ruriko remind her. Eventually Junichi walks a sulking Rihoko home and even pass by and play on the slide where they and Miya played on as kids. After checking the scales that night, she swears to go on a diet.

Rihoko tries her best ice skating with Junichi, unaware that it’s a part of Kanae’s plan to get them together. At school, while Rihoko sends in the Tea Club’s application for the Founder’s Festival, Junichi meets Manaka and Ruriko and helps them carry a kotatsu to their club room. Manaka and Ruriko convince Junichi to help the Tea Club during the Festival and hopes he joins their club as well. On the night of the festival, the Tea Club, wearing Kimonos, serve tea and sake for their guests while Junichi and Rihoko head out and distribute recruitment fliers. After the festival, Rihoko and Junichi go home together where she gives Junichi his Christmas present. Since he has nothing to give her, Junichi grants Rihoko a chance to ask him any favors.

With the festival over and the school cleaning up, the Tea Club invites Junichi for tea as thanks for helping them where the latter gets interested and learns how to make tea from them. While eating at the restaurant where Kaoru works at, Rihoko asks Junichi to accompany her to go the local shrine on New Year’s Eve. But when Junichi and Rihoko are about to go with Miya, the latter two falls asleep, making them go the shrine in the morning instead. As they pray and check their fortunes, Rihoko writes down on an ema Junichi gave her earlier and wishes for a successful diet, new members joining the Tea club, and, as a quick addition, tell her feelings to Junichi someday.

As the new term is about to start and graduation coming soon, Rihoko works hard to recruit people to join the Tea Club before Manaka and Ruriko graduate. During Valentine’s Day, Rihoko gives Junichi a box of chocolate cream puffs. As he eats them, she asks him if there is any girl he would like to receive chocolates from which he in turn asks if there’s anyone she wants to give them. On the day of their graduation, just as Rihoko reports to her seniors that she failed to get any new members, Junichi later arrives and reveals as a graduation present for them, he is joining the Tea Club. In the epilogue set at the new school term, Junichi and Rihoko prepares a Freshmen Tea ceremony for potential members, with Kanae, Manaka and Ruriko also being invited. While enjoying the success of the Tea Ceremony, Rihoko hopes to one day tell Junichi how she feels about him.

Still in pain after being stood up a year ago, Junichi decides to skip the Founder’s festival when Masayoshi catches up with him and invites him at his house. A year later, Junichi decides to change himself, and he starts by volunteering as Tsukasa's assistant for the Founder's Festival committee, to everyone's surprise. Junichi is amazed with Tsukasa's work ethic and the work she does. While being locked in the storage room, Junichi tries to get to know more of Tsukasa until Miya and Sae arrives. On their way home, Junichi meets her older sister Yukari on the way but Tsukasa shows displeasure and hurriedly excuses herself and drags her sister home. The next day, despite Tsukasa being busy substituting swimming classes for Kaoru and Keiko, she is able to help Junichi deal with problems concerning the festival. Later that afternoon, Junichi finds a notebook on the classroom floor. As he tries to find the owner's name inside it, Tsukasa, still in her swimsuit, suddenly arrives.

With the festival behind schedule and Tsukasa's health worrying her, Miss Takahashi suggests they cancel some events, but Tsukasa assures her the festival will be ready unchanged. Knowing that the festival committee is short of manpower, Junichi manages to convince Tsukasa to get their class to help. However, a trio of girls complain and accuses Junichi and Tsukasa's flirting with each other as the root of the festival’s problems. When she fails to end the argument nicely, Tsukasa switches to her real personality and cites the trio’s hypocrisy, silencing and shocking everyone. Later, Tsukasa brings Junichi to the shrine again where she burns her notebook, makes him promise to be hers and seals the deal with a kiss. The next day at PE class, Tsukasa is ganged up by the trio again in dodgeball but the rest of class sides with her, forcing the trio to give up. However at noon, only Masayoshi, Keiko, and Kaoru remains to help Junichi and Tsukasa.

Despite the cheerful atmosphere going into finishing work for the Founder’s Festival in time, Junichi is sad about Tsukasa, and plans to ditch the festival again. But when Masayoshi reveals to Junichi about a girl he never got to confess at grade school, he tells Junichi not to make the same mistake as he did, inspiring him and regaining his composure. At the Festival's after-party, Junichi asks Tsukasa for some time alone, and confesses to her. But when he says that he loves her no matter what her personality is, she, confused and angry, beats him up, telling him she erased the old her for him before crying into his arms when Junichi expresses how glad he is to know the Tsukasa he loves still exists. Miss Takahashi catches the two but decides to leave them alone. Tsukasa later tells Junichi that she began organizing the Founder's Festival as a childhood dream to become Santa Claus herself to make people happy but now realizes she's doing it for her own fulfillment.

A shy girl named Risa Kamizaki confesses to Junichi, which the latter accepts and agrees to become her boyfriend, but she wants to keep their relationship a secret. Junichi wants to go the Founder's Festival with Risa and wishes to introduce her to his friends, but, after some thinking, she refuses. Unknown to him, Risa's reasons for not wanting to come is because at the time when he was getting close with Haruka, Kaoru, Sae, Ai, Rihoko and Tsukasa, she was stalking him and prevented the girls from falling in love with him by showing them a doctored photo that Junichi already has a girlfriend. Later, while visiting the park where he was stood up two years ago, Junichi meets Makihara, the girl who stood him up. To his surprise, Makihara never stood him up because a classmate of hers told her that he was waiting for her at the cinema.