Having been inspired by the school idol group μ's, Chika Takami, a second-year student at Uranohoshi Girls' Academy, tries to start her own School Idol Club. As Chika and her friend Yō Watanabe try to recruit members, she faces resistance from the student council president, Dia Kurosawa, who states she will not approve such a club. Later that day, Chika comes across a girl from Tokyo, explaining to her how she became inspired by μ's, who showed her how normal people could shine. Inspired by her story, the girl introduces herself as Riko Sakurauchi, a transfer student from Otonokizaka Academy, the same school μ's attended. After Yō decides to become the first new member of the School Idol Club, Riko transfers into Chika's class but declines her invitation to her club.
Chika keeps trying to get Riko to join the School Idol Club, only to get rejected every time, while Dia shows a surprising amount of μ's knowledge. Hearing about Riko's struggles with piano playing, Chika and Yō take her scuba diving, where she learns to hear the sounds of the ocean. The next day, Riko decides to help Chika composes their music, encouraging her to write lyrics based on her love of idols. After listening to one of μ's' song's, Riko decides to take up Chika's offer and join her club.
Mari Ohara, a third year student and newly assigned as the director of Uranohoshi Girls' Academy, states that if the girls can fill up the school gym with audience members, she will approve their School Idol Club. Realising that there aren't enough students in their school to fill the gym, the girls are forced to search outside the school to advertise their concert. While trying to come up with a name for their group, the girls stumble upon the name "Aqours" anonymously written on the beach and decide to use it. On the day of the concert, only a handful of students show up, but the girls perform their hearts out nonetheless. Just as a power outage occurs and all hope seems lost, a whole crowd of people, who heard about the concert through Chika's sister and friends, arrive at the gym, while Dia secretly hooks up a backup generator, allowing the concert to continue.
With the School Idol Club approved, Chika and the others begin cleaning up their new clubroom. Meanwhile, Dia's younger sister, Ruby, mentions to her friend Hanamaru Kunikida that Dia used to like school idols, but suddenly came to hate them, leading Ruby to feel that she should not like them either. After Hanamaru looking up school idols herself, she encourages Ruby to join the School Idol Club on a trial basis while keeping it a secret from Dia. As the girls practise running up some stairs, Hanamaru struggles to catch up with everyone, but encourages Ruby to focus on what she wants instead of always worrying about others. Afterwards, Hanamaru convinces Dia to listen to Ruby as she states her true wishes. As Ruby joins the club the next day, she notices Hanamaru's wish is also to become an idol and convinces her to join as well.
As Aquors try to figure out how to improve their idol ranking, Yoshiko Tsushima, who had been absent from school for a while, is struggling to put her chūnibyō habits of pretending she is a "fallen angel" behind her. Watching one of Yoshiko's videos as her persona, "Yohane", Chika decides to invite Yoshiko to join Aquors and have everyone act like fallen angels to increase their appeal. Although this identity gives them a boost in rankings, Dia promptly reminds them that it is only a temporary gain, leading Yoshiko to blame herself. Believing Yoshiko truly loves her persona, Chika once again extends her invitation to join Aquors, encouraging her to love herself for who she is.
Mari informs Dia about plans to close Uranohoshi and merge with another high school due to lack of applicants. When Ruby tells the other about it, Chika decides to follow μ's' example and try to save their school. She decides to make a promotional video to attract applicants, but struggles to find some actual good things to say about their town. As Chika becomes determined to figure out an answer without relying on Mari, she learns that Dia used to love idols, but is stopped from inquiring further by Ruby. Later, as girls from all over town gather to clean up the beach, Riko inspires Chika to get their help in filming their promo video.
With their video placing them in the top 100 school idol groups, Aqours are invited to perform at an event in Tokyo, prompting some concern from Dia. Upon arriving in Tokyo, the girls each check out the specialist shops before coming across the shrine that μ's used to practice near, where they meet another pair of girls attending the event. Later that night, Riko tells Chika about her experiences at Otonokizaka and the expectations she was up against. The next morning, the girls hear about entries opening for the next Love Live before heading over to the event, where the two girls they met before, Seira and Ria Kazuno, are also competing as the unit St. Snow.
The girls are left stunned by St. Snow's performance, even though they failed to win, and the gap between them and the top school idols hits harder when they discover they ranked in last place with zero votes. After some harsh parting words from Seira and Ria, telling them not to treat Love Live like a game, the girls are greeted by Dia upon their return home. Dia explains that two years ago, she once formed a school idol unit alongside Mari and their friend Kanan Matsuura, but when they were invited to perform in Tokyo, the gap in talent left them unable to sing. The next morning, Chika lets out all her pent-up frustrations in front of Riko, with everyone remaining determined to continue being school idols and go beyond zero.
As the girls decide to do something for the upcoming summer festival, Chika becomes curious as to why Kanan quit being an idol. While following Kanan on her morning run, the girls overhear an awkward conversation between her and Mari. The next day, as Kanan returns to school, Chika becomes sick of everyone arguing and tries to confront her, Dia, and Mari about what really happened. While Kanan remains defiant, Dia reveals to the others that during the Tokyo event, Kanan chose not to sing on purpose because she didn't want an injury Mari had to get worse by performing, further revealing that she quit being an idol to stop Mari squandering so many possibilities for her future. Hearing about all of this, Mari properly confronts Kanan, and the two finally manage to make up with each other, after which both of them become members of Aqours alongside Dia, who is revealed to be the one who came up with the group's name.
With the arrival of summer vacation, the girls begin training at the beach in preparation for Love Live while also helping out at a run-down snack bar. Meanwhile, Chika overhears that Riko has been invited to a piano recital that takes place on the same day as the Love Live preliminaries. Alhough Riko tells her that she plans to do Love Live, Chika remains worried about it. After hearing Riko's piano playing for herself, Chika asks Riko to go to the recital, feeling she should also do what she wants to.
After Riko heads off for Tokyo for her recital, the others ask You to take her place alongside Chika in their dance routine. As the two practice together, Mari notices that You has been feeling jealous of Chika becoming close with Riko, encouraging her to be honest with Chika. Later, after You receives a call from Riko telling her how much Chika cares for her, Chika comes over, telling You to dance her own way rather than try to imitate Riko. The next day, Riko performs her recital while Aqours perform at the preliminaries, both managing to perform well.
Aqours qualifies for the Love Live regional qualifiers while Riko wins a trophy in her recital. Despite the popularity of the group, they discover that there are still no applicants for the school. Feeling there is still a large difference between them and μ's, the girls return to Tokyo to meet up with Riko and find out what made μ's so great. There, they meet up with Seira and Leah, who have also qualified for Love Live and state their determination to win. Afterwards, the girls visit Otonokizaka High School, where one of the students tells them that μ's chose to leave no records of their activities at the school. Thinking about these words, Chika comes to realize that μ's was great not because they aimed to be the best, but because they acted freely, feeling that Aqours should aim to do the same instead of just chasing after them.
As the girls keep practicing for the regional qualifiers, some of Chika's friends, having seen everyone's efforts, decide they want to become idols and help the school. Despite almost the entire school showing up to support, Riko reveals that the rules prevent them from joining the group on stage. As Aqours take the stage, they put on a pre-show performance about how they came to be formed and what makes their town so great before performing their song, during which Chika calls down everyone to join in.