Karin is quite pretty, with long wavy pink hair that falls a little past her chest and pink eyes. It is interesting to note that In earlier colour pages of the manga, her hair was a blonder shade, rather than the baby pink it is now.
When Karin was still a baby, her parents were very poor and could afford little to nothing fot baby Karin. For this reason, her father worked extremely hard and became extremely successful and rich. Due to this, Karin, who got everything she wanted, grew up very spoilt and selfish. She demands things to go her way and firmly believes that there is nothing that she will not get in the end. However, despite this, she is said to have a very "pure and honest heart and she can work very hard" and that she is "an extremely good child". Karin often refers to herself in third person, a trait often used to distinguish childishness. She is also very naive to the real world, not knowing the name of her school or what a train ticket was. She also does not know how much things are (as in, average pricing for foods), as shown when she spends all of their money in one day on expensive groceries.
The manga starts with Karin's 16th birthday. Its shows a beautiful layered cake that is adorned with flowers and berries but...Karin's first appearance is of her smashing a piece of cake onto the dining table. She complains to the chef that she told them that she wanted chocolate this year and that she told them not to gicve her vegetables, saying that they made her lose her appetite. When her father tries to calm her down, she simply puts on a sad face saying that "Dad! When I think it's my birthday...I'm so sad!" The next thing you know, Karin is happily eating her brand new chocolate cake.
When she opens her presents, she finds a beautiful dress that "Looks like a wedding dress". When her father tells her that it is for her wedding she competely flips out, saying that she already has somebody that she loves. She threatens to kill herself, saying "Is this what you want Daddy?" However, upon hearing that the suitors name is "Tsuguri" she grabs the folder and looks at the photo. Then she says that she will agree to marry him.
Alone in the hall, she ponders how lucky she is. The "Tsuguri" that she is going to marry is actually her "Tsuguri Sempai " from her school whom she has a crush on. The next day at school, she goes to watch his soccer practice and goes to talk to him, when she is yelled at by their coach he saves her, and tells her that he will see her tonight.:: That night, they finish doing the marriage certificate and paperwork and the next day they are set to be married. The day of the wedding, Karin looks beautiful in her dress. The chaplain asks Tsuguri Nao if he will take Karin as his bride, to which he replies yes. But when Karin is asked, she says "NO, I DON'T" and begins to throw a fit. It turns out that in the chapel, there is only Karin's and Nao's parents and the priest. Karin is upset because she says that for her wedding there should be:
- The whole school invited
- Broadcasted on all channels
- Must have at least 10 sets of dresses
Luckily, Nao is able to pacify her, saying that they'll do that when they graduate and that having people know about this would only cause trouble as people would talk about them. Karin agrees and they get married.
When their parents show them their 'new home' Karin is shocked to see that it is a dirty, run down apartment. However, Nao looks happy and says that it is everything they'll need. When their parents are gone, Nao suddenly moves the furniture, so that there are two bedrooms. Karin is shocked and Nao tells her that she is "collateral damage".
It turns out, Nao married Karin to get away from living in his parents' house, which he seems to dislike very much. He tells her thankyou for marrying him but reveals that he does not care for her. He gives her a set of rules that:
- They are responsible for themselves
- They cook for themselves
- They clean for themselves
- Karin is not to open the door to his room
- They shall not tell anyone at school
- They are free to pursue romantic relationships and fall in love with whomever they please
- If circumstances change they can get a divorce
When Kain tells him that she was the one who agreed to get married, he says that because she chose him based on looks, she was the kind of woman that he "Hated".
Naturally, Karin is quite shocked as she truly liked him. She is left sitting on the floor, outside, alone.
The next morning Karin wakes up exclaiming that it is all a dream. Upon discovering that it's not, she is disappointed but then sees that she has slept in. Wondering why Nao didn't wake her , she realises that he meant every single word of what he said the night before (at first Karin yells at her maid Shimada, before realising she didn't live with them). Karin also realises that she has no Shimada (maid) to wake her up and help her out. When she gets in the shower she discovers that it's cold and she has a difficult time getting her clothes and such. When she finally gets out of the house she discovers that she does not know the way to school. After struggling for hours. Karin finally arrives at school...just as class is dismissed.
Karin's childhood friend Isuzu (or as she calls him Zuzu or Rinrin, depending on translation), asks her what kind of game she's trying to play by turning up so late. Karin responds by asking for food and she is treated by him to two plates of delicious, expensive food. Karin tells Isuzu the story of her morning:
- She didn't know how to get to school
- When she tried to ask for directions she didn't know the name of her school
- She remembered that she forgot her schoolbag but didn't know the way home
- Without eating anything or her phone she managed to get to school.
Isuzu doesn't believe her and asks her why she isn't coming by car like usual. Karin lies and tells him that things are bad between her and her parents so he tells her that she can ride in his car instead. But Karin tells him not to worry because she doesn't wan't him to find out about the marriage.
Karin makes her way to the soccer field and watches Nao play. When they are done she wanders on and asks him to go home with her. But he pretends that he has no idea and says no like he does to every other girl. That night, Karin finally comes home and Nao is waiting for her. He brings her inside to reveal that their home is absolutely trashed. A surprised Karin asks if they were robbed but then remembers that it was actually her (because she did not have a maid cleaning up after her). Nao berates her and tells her to remember to pick up after herself and also to lock the door (she didn't notice the key he left for her).
Karin suddenly collapses, scaring Nao , but it turns out that she is just super hungry. He scolds her and tells her not the make him hate her, at which point, frustrated and sad Karin starts to cry, saying that it is his fault.
She did not know the way home so she waited until his club activities were over so he could show her but he pushed her aside. She wandered around and sweated a lot and mentions she wants a shower but that this one was cold, which surprises Nao because according to him, it's a normal, warm shower. Karin is very upset at this point and so Nao is nice to her and helps her prepare a shower. She sees him walking out of the house during her shower and asks him if he is still mad, he answers no but that she is on 'full display' (naked), making her embarassed.
Nao comes back with some food which Karin eats up quickly and at this point it seems that Nao is warming up to her a little more, though karin hasn't noticed yet (because it's Karin). Nao says that since she was brought up the way she was, he would help her to learn how to do things herself. Karin asks if he would come to like her if she could do everything, but Nao says no. But he also says that he would have a better opinion of her.
The next few days are sort of fast-forwarded and Nao is at his soccer practice when he notices that Karin isn't watching today. He goes home worried but is relieved to see that she is home, she just made dinner for both of them. They eat and Nao says it is delicious, making Karin happy and she asks that they call each other by name. Nao agrees and Karin is really happy, but then Nao sees that she has not put all the money back in the envelope after shopping. He opens it to discover that they only have a few dollars left for the whole month.
It turns out that Karin unknowingly spent all the money because she thought it was for 1 day. She tells him that she will just call her father to ask for more but Nao refuses, he proposes that the two just live like this for 2 weeks, eating only half a slice of bread, green onion rice balls, one boiled egg and a cup of water as seperate meals. He tells her that he should have taken responsibility to teach her these things and that it isn't really her fault. However, Karin calls her father anyway, saying that she'll ask him herself and that she would be worried about Nao . Nao tells her that he would go with her and pats her head. His hand starts to move down to her neck to hug her but Karin (unknowingly) pulls him back to reality, saying that if they are going to her father's house, they can eat all they want tonight.
The next day her father happily greets them and Karin tells her father about an amazing thing called a "train ticket" that Nao showed her. Turns out, Karin tried touching the gates with her hand (because she say other people doing it) and walked right into them. They tell her father everything and Karin apologizes. Karin's father immediately goes into a frenzy of gratitude as apparently, this is the first time that Karin has apologized. He is upset that her mother was not there to see it as she is on holiday. He agrees to give them money and Nao says that he will pay him right back. The two get along as both are business nerds and Karin goes to talk to the kitchen staff.
The kitchen staff accidentally gave her directions to a store with very expensive ingredients. They tell her that they are sorry but Karin has grown up a lot and smiles and thanks them for always cooking delicious food. Nao and Karin's father talk about Karin and both agree that although she is selfish she has a pure and good heart.
Karin's father shows them their room, a single bedroom with a double bed, since he does not know that they have been sleeping in seperate rooms. Karin is happy and takes 3 hours bathing and preparing herself, since they haven't had their "first night" yet but the Nao says that he will sleep on the couch. Karin and Nao talk about why Karin does not hate him even after their circumstances and Nao says that it couldn't possibly be just because of his looks. Karin tells him that it is and what's wrong with that? She tells him her story of how she came to like him.
Growing up Karin always tried finding her prince but could not find one that she liked, when she heard about the popular Nao sempai she went to check it out but because he was playing soccer she couldn't see his face properly with her opera binoculars. She moves in closer and ends up on the field. Nao bumps into her and she almost falls but she catches her and she lands on him instead. When she looks up she sees his face and really like him.
Karin tells Nao to sleep in the bed with her because sleeping on the couch would hurt his back. Nao agrees so they are sleeping on the bed. Karin notices his back, which is broad and moves closer to him. Nao moves and she thinks that he has gone away but he moves up on top of her!