Kotoko, from the lowly F-Class, has a crush on Irie, who is the top-ranked student from A-Class. After two years, she collects her courage and confesses to him and tried to give him a confession letter, only to be bluntly turned down. Irie even goes so far as to say he hates stupid girls (meaning her) and doesn't even read her confession letter. When an earthquake strikes Tokyo, her house is the only one damaged. A friend of Kotoko's father jumps at the opportunity to lend a hand, and in a surprising turn of events they end up living at Irie's house.

Yes indeed, it is the renown Irie-kun's house. After some small talk at breakfast Kotoko and Irie are pushed out the door by Irie's mother,and on to school they walk together. But not happily. Irie-kun soon shows how much he doesn't care for Kotoko-chan, or maybe how little he care for human decency. While riding the train Kotoko-chan get's pushed off at the wrong station by the crush of the crowd. When Kotoko frantically tries to get on the train, the doors close and Irie-kun watches as the train slowly pulls away from Kotoko-chan, leaving her with the only options of running to school or being late. When Kotoko-chan confronts him about his rudeness he simply says for her not to talk to him and that he hates absent-minded girls more than stupid ones. After dealing with all of Irie-kun's cold disdain, she decides to one up him in the upcoming exams.

After Kotoko-chan and Irie-kun had gotten just a little closer, she inadvertently brings embarrassment to the one she loves. Now he will never love her. She falls asleep with tear-stains down her cheeks and her confession letter in her hand. When Irie-kun walks into to tell her it's her turn in the shower, he on impulse decides to read the letter, his face is blank, and void of expression. At breakfast the table is full of talk of the Sports Festival. On a whim the family decides to watch as Kotoko-chan and Irie-kun participate especially since they happen to be participation in an event together.

Geez, Irie-kun's mama is really determine! Kotoko-chan and her friends have made plans to go to Waterland and (only thinking about Kotoko and Irie-kun's future) she sends Yuki and Irie to Waterland just to try to get Kotoko and Irie into a romantic sitsuation! Yeah I know, but anyways on their little trip Yuki tries to observe Kotoko at a closer view, so he asks Irie to go get him some icecream. While Irie's out, to get Yuki's icecream, Yuki switches from the part of the pool where he can stand on the floor , to the part of the pool where Kotoko and her friends are.(where he can't stand) Right when he let's go of the ladder he starts to sink because he can't touch the bottom. Right after he become unconsious Kotoko saves him! During that time, Irie over hears these two girls about a little kid who almost drowned! Next, after he heard he hurried off without the icecream to see if Yuki was okay. When he finally gets Kotoko and the others, he realizes that Kotoko took very good care of Yuki, so he just stands there and smiles! Soon after that Kotoko decides to take everyone to the Waterslides and when its her turn to go down she goes. Once she starts going down, she gets a leg cramp, which paralyzes her so she can't move! Once she get to the bottom of the waterslide, Irie notices that she's having a hard time getting out, so he pulls her up and out of the water just in time, and gives her foot a relaxing foot rub!

The final exams starts next week, and the results decide whether or not the F-class students make it into college. After having recieved prior assistance from Naoki with her and her friends' schoolwork, Kotoko is asked - commanded, rather - to get Naoki to tutor the whole of Class F so they can pass their finals.

With Naoki's help, the whole of Class F passes their finals (with the exception of Kinnosuke.) Kotoko tries to give Naoki some homemade chocolate but fails to do so. Later on, Naoki is set to take the entrance exam to Tokyo University. Kotoko sets off to accompany him to the venue; however, the plot twists when Kotoko's health takes a turn for the worse.

Having missed the entrance exams for Tokyo University, Naoki decides to go with the school's escalator system. Graduation day's rolled round and soon after that, the F and A classes bump into each other during their farewell dinners. An exchange of heated words soon ensues where Naoki puts Kotoko down in front of everyone, upsetting her greatly and forcing her to do something drastic - which in turn yields an unexpected outcome.

The first day of college has finally arrived, but Kotoko can't stop thinking about her first kiss with Naoki! What does this mean for their relationship? Just as she thinks she's finally secured a place in Naoki's heart, an obstacle arises in the form of Yuuko Matsumoto, bishie extraordinaire.

Joining the tennis club turns out to be the worst decision of Kotoko's college life. The grueling practices, the painful injuries and the complete feeling of incompetence would be worth it...if only Naoki would show up to practice!! Meanwhile, Kotoko works up the courage to ask Naoki to the latest "couple's movie", but of course Naoki flat out refuses. Kotoko decides to go to the movie anyway but is shocked to see Naoki there with none other than Yuuko Matsumoto!? Can Kotoko really compete with someone so perfectly matched to Naoki?

Kotoko's father has decided that him and Kotoko have overstayed their welcome, and so the time has finally come for Kotoko to leave the Irie's! How will Kotoko manage? Has she lost her only advantage to winning Naoki's heart!?

Naoki begins thinking about what he wants to do with his life and about the future of the family business. For spring break, Kotoko and Sudou go to Romance Village to be closer to Naoki and Matsumoto. However, the experience isn't as "romantic" as it may seem.

Irie tells his father he does not wish to take over his company, instead he wants to become a doctor. Irie's dad has a heart attack after he hears this. When the company employees come to see Irie senior in hospital, one of them requests a marriage interview with Irie. Irie meets Chris and decides to marry her. Kotoko decides to give up on Irie after she overhears him telling oba-chan that he likes Chris. Kotoko goes on a date with Kin and he officially proposes to her.

Worried over how to answer Kin, Kotoko talks to her dad about what he thinks about her getting married to Kin. Kotoko's father suggests that they leave Irie's place, Kotoko agrees. Irie brings Chris home to meet his family, Oba-chan acts very stuck-up, even Yuuki doesn't seem to be too happy about Irie marrying Chris, he confronts Irie and comments that Irie is in love with someone else. Oba is very upset while talking to her husband in hospital saying she was sure Irie loved Kotoko but now he's marrying Chris, Yuuki comes in and claims that the only one Irie-kun loves is Kotoko. Kotoko skips Tennis to go and see Kin and plans to say yes to his marriage proposal. Kotoko's two friends catch up to Irie and Matsumoto talking and explain that Kotoko is not with them because she went to see Kin and give him an answer since he proposed to Kotoko. when Irie hears this he runs off somewhere. meanwhile Kin requests Kotoko's answer but she is unable to give him one, and asks for more time, Kin gets angry and says he will force Kotoko to forget Irie, and as Kin grabs onto Kotoko she yells 'Irie-kun'. Kin falls to the floor crying while Kotoko runs out into the rain

Kotoko feels guilty for having led Kinnosuke on. As she walks in the rain, she encounters Irie-kun, who is holding an umbrella. He confesses his love for her, and they walk home holding hands. Irie-kun announces his proposal to the Irie family and to Kotoko's father. After getting permission, he ties up all the loose ends with his father, Chris, Kinnosuke, and Chris' father. Irie's mother rushes their wedding, and they get married within two weeks of Irie-kun's proposal.

Now married, Kotoko and Naoki head off to Hawaii for their honeymoon. They soon become accquainted with fellow newlyweds Horiuchi Mary (Mari) and Takumi. Things start to get ugly when Mary decides to interfere with Kotoko and Naoki's relationship.

Chris is about to return to England, but still harbours strong feelings for Kinnosuke. Feeling sympathetic towards Chris, Kotoko decides to help her in her quest to win Kinnosuke's heart. However, things don't quite go out the way they should...at least, initially.

It's Kotoko's first day of learning how to be a nurse and she meets and befriends 4 new people: Ogura Tomoko, Shinagawa Marina, Kamogari Keita, and the lovable Kikyou Motoki(Miki). She then finds out that Marina, Motoki, and Tomoko all love Naoki. And all hate his wife who happens to be Kotoko. Unable to bring herself to say she is Naoki's wife she plays along with their plan to find out out who Naoki's wife is. Later on they go to Naoki and Kotoko's house and try to find out who it is. Kotoko fustrated with keeping the secret is about to tell them that she is Naoki's wife, however all three of them see Naoki walking up to the house with Mastumoto Yuuko and of course believe she is Naoki's wife. Astounded by her beauty and class Marina, Motoki, and Tomoko give up on Naoki, leaving Kotoko unhappy about the fact that they think Yuuko is Naoki's wife. The next day however Naoki comes into her classroom and tells her about some shopping requests. When he leaves, everyone is speechless and Kotoko begins apologize for deceiving them. However finding out that Kotoko is Naoki's wife, they are filled with joy and now have their hopes up again. Later at dinner, Marina, Motoki, and Tomoko group around Naoki while Kotoko is drinking with Keita. After yelling at Keita, due to being drunk, she falls asleep. Naoki is about to take her home, but Keita, furious about Naoki not caring about Kotoko's needs, yells at him. The next day when Keita sees Kotoko working as hard as she can, he lets her use his arm to practice on blood pressure. While Kotoko is getting ready, Keita begins to blush showing he has feelings for her. At the end of the episode Naoki sees Keita and Kotoko together and begins to get jealous.

Kotoko is still learning the tricks and trades of becoming a nurse. Kotoko faints during an practice autopsy which results in Keita saving her. Naoki sees this and decides to confront Keita. Keita however strongly believes that Naoki treats Kotoko with no respect and ignores Naoki's words. Meanwhile Naoki's mother seems to notice that Keita is much more chivalrous to Kotoko than Naoki and decides to find out more about him. After gaining information from other students, Keita is just a nice guy and even Naoki's mother believes that even she would choose Keita over Naoki. The end of the episode shows Keita concerned about Kotoko going back to Naoki, and asking her to leave Naoki for her own good, as he believes Naoki does not love her.

Irie-kun starts to ignore Kotoko due to being overly jealous of Keita, when Kotoko gets very fed-up of his behaviour she gets very upset and starts throwing books at him and saying that Keita was right Irie doesn't care about her and that Keita thinks about her more then Irie does and that Keita was serious, Irie slaps Kotoko, Kotoko yells that she's had enough and runs away, she ends up at Tomoko's house. Kotoko's dad talks to Irie about how things had been between him and Kotoko's late mother. The next day in the lunch room Keita talks to Kotoko asking her to live with him now that she's run away from home, when Kotoko declines Keita confesses that he is in love with Kotoko, and she should not go back to someone who does not love her, Kotoko tries to defend Irie but Keita questions if Irie came after her, and just as Kotoko is feeling like Keita is right, Irie runs in claiming Keita is wrong and that he was only being the way he was because he was feeling jealous of Keita, explaining that he (Irie) has never felt jealous or sad before so he didn't know what to do, he confesses that he can work through it all with Kotoko by his side, Kotoko still teary, questions Irie if its ok for her to be by his side, Irie smiles at her saying that's what he wants, Kotoko runs to him, the whole school breaks into cheers and congratlates them. Later, Irie is seen kissing Kotoko in their bedroom.

When Kotoko announces to Irie that during the capping ceremony/graduation all the male students in the medical department are to present flowers to the nurses they like, he tells Kotoko that he won't be able to make it to the ceremony because of a meeting and that the whole flower giving idea was stupid. Then Kotoko is selected as the representative for her class and has to recite the Nightingale Pledge because she is Irie's wife and because nobody except Moto volunteered but since the head nurse knows that Moto is a male and the tradition was to have female nurses to recite the Pledge, he wasn't selected. Afterwards, Kotoko practices memorizing the Pledge but has trouble when Moto walks by reciting the entire Pledge perfectly. At that moment, Kotoko realizes that Moto really did want to be a female nurse because...

Nobuhiro turns out to be Yuki-kun's friend Non-chan from back when Yuki was admitted into hospital.However, he has changed very much due to his lonliness from growing up in the hospital. Kotoko manages to talk to Non-chan and makes him realize how many people care for him.

It is Kotoko's birthday and Irie takes her out for the night. Irie and Kotoko are very 'lovey dovey' in this episode. Irie and Kotoko pull an all-nighter at the hospital as a lot of emergencies came in, Kotoko stayed even though she seemed to have a fever. When Kotoko returns home in the morning, Oba-chan looks worried over her appearance and asks her if she's alright, Kotoko thinks she's running a slight fever, but Irie asks everyone to wait a moment, he asks Kotoko if she's pregnant, Oba-chan and Yuki both get a shock and yell 'what!'.The episode is left at a cliffhanger.

After visiting the hospital, it is confirmed that Kotoko is indeed pregnant. Oba-san throws a party, Kotoko's and Irie-kun fathers both look up baby names, even Yuki is excited though he tries not to show it, but is later seen with toys for the baby. After the party, Kotoko-chan and Irie-kun enter their bedroom, Kotoko is a bit worried and questions Irie-kun on what he thinks about her being pregnant, if he's happy about it or not. Irie-kun calls her an idiot and hugs her saying he is very happy. Going into work, Kotoko's friends put her into doubt about Irie-kun's loyalty to her. As Kotoko spies on him (with Oba-san spying on both Kotoko and Irie-kun) she sees him talking and laughing along with a young nurse. Kotoko then sees Irie-kun talking to Yuuko Matsumoto who it seems...

The episode begins with Kotoko messing around with her C-cup breasts. She later on goes to see Kin-chan and finds out that Chris is 3 months pregnant. Kotoko, after coming back home, tells Irie-kun about the news. She later doesn't feel good and thinks it is because of the iron tablets she's been taking to replenish her blood. She doesn't tell Irie-kun about this because she doesn't want to disturb him while he's writing this thesis. The next day, Kotoko and her friends are discussing when Kotoko is going to take maternal leave. She refuses quickly, stating that she wants to work as much as possible and goes to see Irie-kun. Later on, her friends from work go home and leave Kotoko to walk home with Irie-kun but he informs her that he will be working late that evening as he wants to do more of his thesis. It then shows Kotoko on the tube where she thinks that she feels a bit light-headed. As she is walking up the steps from the tube she collapses at the top not feeling well, she is spotted and then an ambulance is called, Kotoko is unconscious. Irie-kun is then seen writing when his mobile phone starts ringing. We seen him running through to the hospital where Kotoko is, all the family are there. It turns out she was excerting herself too much during pregnancy. One month later Kotoko presuades Irie-kun to go to Pregnancy Classes with Kin-chan and Chris. It's there where she goes into labour. Kotoko, Irie-kun and Oba-san are at the vending machines at the hospital when Matsumoto is rushed in with Sudou. She has been coughing up blood due to her illness. Irie-kun has no option but to operate and thats when Kotoko gives birth, Irie missing it. They have a baby girl and call her Kotomi. It then shows a few years later and it is clear that Kotoko and Kotomi are rivals for Irie's love. It ends flicking through scenes of the friends and family of Kotoko and Irie-kun.

Kotoko,Naoki and their daughter Kotomi go to Naoki's grandparents home. On the train, Naoki has a flashback to when he and Kotoko went there after their marriage.