Kaori Fujimiya (藤宮 香織 Fujimiya Kaori) is the female protagonist of Isshuukan Friends and Yuuki Hase's classmate. At the beginning of the series, she is always alone and does not seem to have any friends. This can be attributed to her chronic memory loss, which causes her to lose all her memories of the times she was happy and of those she considers friends every Monday. Despite her efforts to resist Yuuki's advances to become her friend, she will not forget him as well. She eventually warms up to him and they become close friends.
Kaori is a beautiful and cute young girl who has amber eyes, light chestnut-brown hair falling freely to her shoulders, with several tufts tucked around her left ear and her skin is very fair. She is typically seen wearing the standard girls' uniform for their school, consisting of a collared brownish-black sweater, a turquoise bow at her chest, a light brown skirt, black knee-length socks and white and blue indoor shoes.
When she was younger, she was involved in a car accident, which caused her to lose her memories of all those she considers friends by the end of the week. Because of this, she makes it a point to maintain a cold and withdrawn facade in front of others, using this as an excuse not to make any friends as she fears losing them.
Outside of class, however, she is warm, kind, and innocent, and Yuuki further helps her break out of her shell. Gradually, under his guidance, she manages to gain more friends and starts to act more like her usual self in class. She has shown a remarkable progress in mathematics, and is in charge of that subject for their class.
Prior to the beginning of the series, Kaori was relatively popular in primary school, as her pleasant disposition made her amiable and easy to get along with. She was close friends with her classmate Hajime Kujou, and the two made a promise to meet up at the park the day before he transferred to Hokkaido. However, when rushing to meet him, she was caught in a car accident and therefore never fulfilled their promise. This accident later spurred her memory loss issue, and she started to forget all those around her whom she considered friends at the end of each week, though her memories of her families and normal acquaintances remained intact.
To counter the pain of becoming emotionally connected to others and subsequently losing them through her affliction, Kaori decided to detach herself from others as much as possible, hence erasing her chances of making any more friends. This led to her being both alone and the target of her classmates' gossip.
She catches Yuuki's eye as her cool exterior intrigues him. The series opens with Yuuki's attempts to make conversation, though she pulls away every time, feigning a cold when he tries to talk to her as they assist the teacher in carrying books. She repeatedly tells him they cannot be friends no matter how much she wants them to be, but this does not sway his resolve. His first measure to reach out to her is to have lunch with her on the school rooftop every day, and it works after several times. She subconsciously lets down her guard around him and confesses her secret of her memory loss, growing emotional when she realizes she will forget his kindness toward her as well. However, he insists that he is willing to befriend her as many times as he has to, as long as she isn't alone anymore. He stays true to his word, asking to be her friend again the following Monday when her memory resets.
They plan a friend outing, in which they have lunch together and subsequently an enjoyable karaoke session for the first time in her life. Yuuki notices from her mannerisms how clear it is she has not been out with a friend for a long time. They ride the train together afterwards, and Kaori alights with tears in her eyes, asking that he tell her everything that happened the next Monday.
After the memory loss cycle repeats several times, Yuuki comes up with the idea of disclosing her secret to Shougo, explaining it would be useful have him help think of a solution, and she agrees after some hesitation. When Shougo unexpectedly suspects her of lying about her condition and calls Yuuki naive for believing her, Kaori, who has been silent the entire time, speaks up to affirm the reality of her condition. While Shougo eventually comes to believe her, he still regards her with the same aloofness as usual, and tells her he won't understand or trust anything unless he hears it directly from her.
Later on, Kaori returns to the classroom to retrieve her diary which she left under the desk, only to hear two of her classmates gossiping about her. Distraught, she stresses over whether or not to confront them, but Shougo steps in before she can react, commenting offhand that they have bad taste and retrieving her diary for her. Despite what he said earlier about not minding if they were friends or not, he calls her his friend, though later denies actually meaning it. He does not make much of an attempt to console her, but instead advises her to cry in private so as to prevent further gossip about her, and she notes silently that she now knows why Yuuki trusts him. His earlier words about her having to speak up for herself to make her stand come back to her just as he leaves, and she confronts the gossipers by saying she has friends too before leaving.
When Kaori lived her daily life in solitude, avoiding making friends as much as possible because of her memory loss, Yuuki was the first to reach out to her. Although she initially regards him with the same cold, detached air as she does to everyone else, he is not deterred and continues trying to befriend her by having lunch with her every day on the school rooftop. Touched by his sincerity, her mask begins to crack and they fall into a friendly relationship, growing even closer when he brings her out to experience things she never could without a friend. As she forgets him after the first week of their friendship, their bond is very strong and he is of great importance to her. Yuuki constantly refuses to give up on Kaori, even when her memories of him are reset every Monday, saying that he will befriend her over and over again as many times as he has to.
As Kaori's mind is innocent, she remains oblivious to his hints of romantic feelings toward her, although even Shougo and her mother notice them. It is hinted that she has some romantic interest in Yuuki when she explains to Shougo that she felt something in her chest when she saw Yuuki talking with other girls, but of course she doesn't know that the feeling is jealousy so she doesn't know how she feels. This shows the progress of their relationship and how her memory problem is being healed. She keeps a diary, in which she records her conversations with him (and later other friends) in great detail, so she can remember him every week. As he is especially weak in mathematics, her strongest subject, she can sometimes be seen tutoring him.
Yuuki's affection for Kaori has been shown to be bordering on possessive at times. When she loses her diary and therefore not only cannot remember him, but also has an abysmal impression of him, he willingly drops everything to search for it. He cares deeply for her (and what she thinks of him), fretting when she falls sick and preventing her from entering the grass by saying that the blades are sharp and might hurt her. He is also easily made paranoid and slightly jealous, especially when she focuses too much on his friend Shougo, though he never acts on these adverse feelings.
In the second semester, the transfer student Hajime jars her memory once more with his cutting words, causing her to faint and Yuuki to panic. He swears to protect her from Hajime after he makes it clear how much he dislikes her. She loses her memories of Yuuki once again due to the trauma of her past, reverting their relationship back to that of the first reset.
In spite of that, after her memory returned, she is still willing to continue being friends with Yuuki.
At first, Yuuki introduces Shougo to Kaori in hopes that he will be able to accept her situation and they can cooperate to find a solution; however, the ever-cynical Shougo instead accuses Kaori of lying about her condition to deceive Yuuki. Even after the misunderstanding is cleared up, they are by no means close, as Kaori is intimidated by Shougo's aloof demeanour, and he in turn states that he doesn't care whether or not they become friends. In spite of this, he still intervenes when their classmates are gossiping about her, retrieving her diary for her when he knows she can't face them and referring to her as his friend in the process (though he later claims he only said it as "friend's friend" was too cumbersome). He also demonstrates worry when Kaori faints during her brief reunion with her childhood friend Hajime. He indirectly inspires her to have the courage to speak up for herself and become as assertive as him so that others will take her seriously.
Even so, deep down, she still doesn't consider him a close friend, as she remembers him every week without fail while forgetting Yuuki and even Saki, whom she meets much later. However, she respects him for his academic prowess. When Saki's attempts to draw them closer fall flat, the former laments that their personalities make them incompatible: one is too stoic, and the other is too shy. Their interactions usually comprise Kaori being awkward and Shougo being bored, though she is able to converse naturally with him during the first reset since their first meeting.
Multiple times, Shougo and Kaori's uncertain relationship involuntarily fuels envy and insecurity on Yuuki's part, as he fears he will steal her from him. This is dismissed by Shougo, who states he has no intention to make a move on her.
As appears to be the case for most of Kaori's friendships during the series (with the exception of Shougo), Saki approaches her first and asks to be her friend right off the bat, catching her off guard. Saki respects and idolises Kaori; she was bullied due to her small stature in primary school and became overly dependent on others as a result, in contrast with her self-construed image of Kaori, in which Kaori is cold because she is independent and does not require anyone's help. Thus, she looks up to her and mistakenly assumes that they are one and the same with their memory loss problems, despite Kaori's attempts to correct her. While they have not known each other for long, they address each other by their first names, a sign of familiarity or informality, and Kaori forgets her after the first week of knowing her.
In primary school, Kaori and Hajime were relatively close friends, and they made a pact to meet up at the park the day before he left for Hokkaido—a pact that she never kept her end of, as her accident kept her out of commission and therefore not in any condition fit for movement. However, this resulted in a grave misunderstanding between her and Hajime, as he mistakenly assumed that she did not value him as a friend, and left with a heart simmering with resentment. This resentment carries on to several years later, when he returns and rejoins her class as a transfer student, coincidentally assigned the seat beside her. He regards her with scorn and reproach, calling her a traitor and causing her to faint. While this surprised him, his dislike of her remains, and he expresses clearly to Yuuki that he wants nothing to do with her.
- She is good in making fried eggs. She always makes the fried egg #7 which Hase likes.