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Haruna who devoted herself to softball decide to find a boyfriend in high school by instruction from Yoh, who is willingly to teach her how to get a boyfriend but with only one condition, don't fall in love with him at all.

Similar to Forget Me Not (2015), One Week Friends takes the viewer to a high school where a boy is fascinated with and falls for a cute class-mate of his. The girl is a loner who has no friends. She gets approached by class-mates and is asked to after school activities, but is resolute in always saying 'no.' She has amnesia and only remembers events, names and faces one week at a time. Not to be put off her class-mate is determined and even comes up with a clever idea for them to remain friends and acquainted.

Arata Kaizaki is 27 years-old and unemployed. He quit his prior job after working for the company for 3 months. Arata Kaizaki decides to take part in a research program "ReLIFE." He takes medication that makes him look 10 years younger and he is to attend high school for a year. There, he falls in love with female high school student Chizuru Hishiro.

Seventeen year old high school student Rio Ozawa is always the center of attention due to her beauty. Yet Rio has never cared about anyone but herself due to her traumatic past. Her friends exist only so she can use them for her gains. Rio is only interested in money. She is involved in "compensated dating" and extortion. One day Rio's photographs get mixed up at the store with those of another person of last name Ozawa. She then meets 35 year old college professor Kouki Ozawa, and falls in love for the first time. Rio feels confused by her emotions. She changes from a confident, mature person, to something more like a typical schoolgirl with a huge crush. She follows Kouki around, asks him to tutor her, and wants to date him. Although Kouki becomes interested in Rio, there is a reason he doesn't pursue the relationship. However, Rio is very insistent and starts changing her whole world for the better in order to be with him. Suddenly Kouki disappears without saying goodbye, and Rio is crushed. Her friends, with the help of Kouki's relative, find him working at another school. Rio then finds out that he is dying of brain cancer, which is why he wanted to keep his distance, in order to avoid breaking her heart. She convinces him to get a risky operation, even if it means he cannot remember her, so that they can have more time together. In the end, he survives the operation, and they get together again, though it isn't clear if he remembers her.

A schoolgirl is not doing well and her English marks are sub-par. A teacher asks her to attend after-hours tutoring in order to improve her grades. Jealous of the attention she finds herself bullied and resented, but she develops feelings for the teacher when he rescues her. At the same time, a female teacher is trying to gain the attention of the male teacher the schoolgirl has fallen for. Will they end up together or does fate separate the student and the teacher?

Aoi and Riku, who have been friends since they were five years old, are part of a band with other students at the university they attend. Riku is known as being unflappable and "perfect" to fellow band members. Rifts and misunderstandings in the band, Strobocorp, lead to a misfired performance on Aoi's birthday at a local festival, after which she has a tragic accident. She awakens to find herself re-living the prior week before the problems emerged, and Riku reveals that he can turn back time. He explains that he has been doing this for years, allowing him to perfect his apparent abilities. They admit to each other that their feelings go beyond friendship as they repeatedly relive the past.

A girl receives a letter and upon opening and reading it finds a narration of the events of her day including the arrival of a transfer student suffering from challenges. The letter is from herself ten years in the future. She has advice for herself on friendship, school and life. This is the catalyst for her friend and her becoming better versions of themselves.

A girl that resemble "Sadako" of the movie Ring is being feared by her classmates. She is avoided by everyone.While everyone is avoiding her, the popular boy Shota Kazehaya befriends her, and their love begins to grow.

Momo Adachi is a female high school student. She appears to be a wild girl due to her tan skin and dyed hair, but she is a actually naive and sweet student. Since her days in middle school, Momo Adachi has secretly held feelings for classmate Toji. Meanwhile, the most popular male student, Kairi Okayasu, becomes interested in her. Her friend Sae is jealous of her and tries to block Toji from Momo. Momo is conflicted with Toji and Kairi, but she has to make a decision.

As a child Takuma is diagnosed with a heart condition that requires care from a cardiologist. He soon becomes friends with his doctors young daughter Mayu while being treated at the hospital. One day Mayu overhears her father saying that Takumas condition is serious enough that he most likely wont live beyond the age of 20. Takuma isn't aware of this himself, however, so at 8-years-old he makes a promise to marry Mayu when they turn 20. Later in life, Takuma becomes aware that he wont be able to keep this promise and he begins distancing himself from Mayu in hopes of protecting her.

Aoi Nishimori's parents moved to another city for work, but Aoi didn't want to transfer to a new high school. She stays behind and lives in an apartment by herself. Shusei Kugayama moves in next to Aoi's apartment. Shusei is a very popular student at their high school. Due to a mistake, Aoi makes the sprinkler go off in his room. Until Shusei's room is fixed, he stays with Aoi.

Mika is a fresh high school student who starts texting a mysterious boy. She is shocked when he reveals who he is - Hiro, a delinquent attending her school. What she doesn't know is that Hiro isn't as bad as he seems.

Hibiki is an awkward, 17-year-old high school sophomore who hasn't known romance. But she's about to fall in love for the very first time. With whom? A man who isn't great with words, but compassionate about his students. It's her history teacher, Mr. Ito. "Is it okay if I fall for you?" Hibiki asks. "I'm afraid I can't return those feelings," is Ito's reply. Hibiki's first love crashes before takeoff. But it doesn't matter. "Still I want to cherish my crush anyway." A teacher's heart begins to turn by a student's pure love.

When she was in middle school, Yoshioka Futaba met Tanaka Kou whom she had mutual love. After Kou moved to Nagaski with his late mother, Futaba lost contact with him. In her first-year of high school, she met Kou who's now carrying the name "Mabuchi", who is now stoic, cold, and totally different from the gentle Kou he met in middle-school.

Hikaru Tsutsui is a high school student. He enjoys animation and video games in the virtual world, but he doesn't enjoy his real life. People at his school don't even know he exists. One day, he cleans up the pool at his school with beautiful Iroha Ikarashi. Iroha approaches Hikaru and confesses that she likes him.

Natsume - a teen fashion model from Tokyo - feels empty inside after having moved into a country town with her family. One day, she meets Koh, heir of Shinto priest family ruling the area and finds herself falling under the spell of this selfish yet handsome boy, who makes her realize beauty and desire she has. Cursed by fate, a traumatic incident at the local summer festival breaks their ties. She gets over the incident and Koh gradually; however, no matter how she steps away from Koh, she cannot forget his dazzling world and the dream Natsume had. Can they find their love against the fate? Can Natsume find her desire for the future?

Ryota and Koharu are high school students. Ryota is indifferent to people and says very little. Koharu is not afraid of to speak her mind and she has a bright personality. Since a game of rice bag jump, they begin to date. They date at a fast-food restaurant, realize they love each other at a family restaurant and finally swear their love on a dining table with white rice.

Sayaka works as a property agent. One day after work, she finds a man, named Itsuki, collapsed outside her house. She takes him in and they start to live together. Itsuki teaches her about cooking and plants, but holds many secrets.