With a new school year approaching, Honoka succeeds Eli as student council president, with Umi and Kotori as her aides. Word soon reaches the gang that Love Live is taking place yet again on a larger scale then last year. However, since the format is now changed to include regional preliminaries, they soon realise that in order to qualify for the tournament, they would have to beat A-Rise in their regional preliminary. The gang is taken aback when Honoka suggests they don't need to enter Love Live!, feeling it is not something she would say. Later that night, Yukiho informs Honoka that the opening date of Love Live is at the end of March, when the new school year begins. The next day, as Nico challenges Honoka to a race to decide if μ's should enter Love Live or not, Honoka comes to understand the meaning of those words, as at that time, Eli, Nozomi, and Nico will graduate and no longer be school idols, making this year's Love Live the last opportunity for μ's to perform together as a group of nine. With the others easing her worries, Honoka states her true desire to enter Love Live and aim for victory.

A new rule is introduced to Love Live in which contestants in the preliminary rounds must perform songs that haven't debuted yet, so μ's decide to hold another training camp at one of Maki's villas in the mountains in order to come up with a new song. As Maki, Umi, and Kotori find themselves in a creative slump because of the pressure, the girls form camping groups of three to help them come up with ideas for music, lyrics, and costumes, but even then they have trouble keeping focused. However, after hearing some encouragement from their friends, Maki, Umi, and Kotori gain the drive to come up with a new song overnight.

With various alternatives to performing on one of the main stages for the Love Live preliminaries, the girls consider streaming from within their school, though realise it'll be harder to appeal to voters that way. With help from the broadcasting the club, Honoka, Umi and Hanayo use the school's broadcast to both spread word of their performance and give themselves more practise. Whilst trying to find a suitable location to perform where they haven't already performed before, the girls are brought to UTX Academy by the members of A-Rise, who have been keeping a close eye on each of μ's' members. After stating their intention to not lose against them, A-Rise offers to let μ's perform on their stage atop of UTX Academy's roof for the preliminaries. As the girls feel doubtful after seeing A-RISE's performance, Honoka pumps up the other girls whilst the other students come to show their support as μ's performs the new song they created together.

After an agonizing wait for the results, μ's are delighted to discover they have qualified the first preliminary round, along with A-RISE. As the girls strive to practice hard for the next round, Nico seems to be preoccupied by something, so the others decide to follow her, though she ends up spotting them and escapes. Whilst wondering what Nico is up to, they end up meeting her younger sister, Kokoro, who, along with her siblings Kotaro and Koko, has been led to believe that Nico is the star of μ's and the others are merely her backup dancers. After finally being pinned down by the understandably bemused girls, Nico explains she has been skipping practice to look after her siblings whilst their parents are away, stating that she has been telling them she was a super idol from the beginning. Nozomi believes she has kept this front up even after her attempt at being an idol during her first year fell apart, as she didn't want to destroy their vision of her. Upon hearing about this, the girls arrange for Nico to give a special performance for her siblings, claiming it to be her last performance as a 'solo idol' before joining her fellow idols as equals in μ's.

Whilst Honoka, Umi, and Kotori are on a field trip to Okinawa, Rin is assigned as temporary leader of the group as they prepare for a fashion event at the weekend. However, Rin isn't confident in herself and struggles with the responsibilities. As Rin feels she is unfit to be leader, thinking she isn't cute enough, Hanayo tells Maki about how Rin has a complex about her boyish looks, which she was often teased about during elementary school. With bad weather leaving Honoka's group stranded until after the fasion event, Rin feels she isn't cute enough for the fancy dress given to the center and passes on the role to Hanayo, though the others can tell she is bothered about it. After Hanayo speaks with Honoka, the group arranges for Rin to wear the dress whilst everyone else wears butler outfits, feeling it fits her the most. The fashion event turns out to be a success and Rin ends up being more confident about expressing her femininity.

Both μ's and A-Rise are invited to appear in a Halloween event in Akihabara, with μ's hoping to make a big impact to gain support for the Love Live preliminaries. Thinking they need a new look to provide that impact, the group tries various methods to accomplish, such as changing their outfits, impersonating each other, and even trying out a rock look, but nothing seems to work out. On the day of their performance, Honoka realizes they don't need to change themselves, as they already have quite varied members themselves, and they perform together with their natural abilities. Meanwhile, Yukiho comes across a shocking letter whilst rummaging through Honoka's room.

Upon reading the results of her physical exam, Honoka discovers she has put on weight, with Hanayo also shown to have gained weight too. Both Honoka and Hanayo are put on a diet whilst Umi and Kotori help sort out Honoka's student council duties. However, Umi soon discovers the two had been sneaking off during their runs to eat rice. Things get worse when a blunder by Kotori causes a budget request from the Art Club to be approved ahead of a meeting, becoming met with resistance when they attempt to withdraw it. Despite Eli offering to help, Honoka and the others decide to sort out the crisis themselves, apologizing for the mix up and sorting out a budget draft for all the clubs. In the process, Honoka manages to get back to her old weight, with Eli and Nozomi left assured that the student council is in good hands.

Honoka announces at an interview that μ's will be sure to win against A-Rise in the final Love Live preliminaries. Nico proposes they should perform a new song at the preliminaries and Nozomi suggests making it a love song. The group has trouble producing the song, for none of them have any experience with love. They go as far as to watching a romance movie for reference, however Maki says that these halfhearted efforts to write a new song will lower the quality of their performance. Maki follows Eli and Nozomi to Nozomi's home, where she learns that Nozomi's wish isn't to write a love song, but rather to perform a song that all of μ's wrote together. Nozomi explains that she didn't have any friends at school before meeting Eli, and that the formation of μ's allowed the nine of them to be connected and share the same feelings. Nozomi says that it doesn't matter if they aren't able to create the song, since the nine of them being together is already a miracle. Maki and Eli call over the others, deciding to go ahead with writing the song. It soon begins snowing, and the girls run outside. Each and every one of them catch a snowflake, and are lyrically inspired.

The day of the Love Live preliminary finals arrives, with the girls overcoming the cold weather to get together to the stage. However, Honoka, Umi, and Kotori are held back by a delay on an address they are giving at the school and become snowed in. Determined not to let their efforts go in vain, the three girls decide to head to the stage on foot, finding that all of their fellow schoolmates have cleared the path for them. Rejoining the others just in time, the girls of μ's take on the feelings of all of their supporters and perform the song that they all wrote together.

On their way to the local shrine to celebrate the new year, the girls run into A-RISE, who congratulate them on winning the Love Live preliminaries. Meanwhile, Eli, Nozomi, and Nico, who are helping out at the shrine, worry about when it will be time to graduate. With μ's needing to make an impression to give them an advantage during Love Live, Hanayo suggests they come up with a group catchphrase for the official website that best represents the group. Later that day, Honoka is approached by A-RISE's leader, Tsubasa, who had been contemplating over how her group lost to μ's, leaving Honoka wondering the same thing. The next day, the girls get together at Honoka's store to make mochi for all of their supporters, though come no closer to thinking of a catchphrase. Later, upon encountering people's emas at the shrine giving their support for μ's, Honoka comes to understand the group's driving force came from everyone's support and decides on the catchphrase, "The story we all realize."

After she and Alisa pass the entrance exams for Otonogizaka, Yukiho asks Honoka about what will happen to μ's after Eli, Nozomi, and Nico graduate. With the girls divided between whether or not μ's should carry on with new members in the new year, Eli states that Honoka and the other younger members should be the ones to decide what the future of the group will be. Later, Alisa, who had originally wanted to join μ's upon entering Otonogizaka, tells Honoka that she instead intends to form her own idol unit with Yukiho, having realized that the reason she loves μ's is because of its nine members. Later that weekend, Honoka brings out the group to play, visiting all sorts of places that each of the members decide to go. Upon arriving at the beach, Honoka and the others announce their decision that μ's will disband after graduation, with everyone feeling the same way that a group with even one member missing is not μ's at all. After letting out all of their tears, the girls return home and make preparations for their final performance together at Love Live.

Following the drawings for performance order for the Love Live finals, it is decided that μ's will be the last performers of the event. After finishing what could well be their final practice together, the girls find it difficult to part ways and instead decide to have a sleepover at the school. That night, the girls go up to the rooftop to see the city lights, feeling proud that they became school idols. The next day, the girls arrive at the venue for Love Live finals, stepping out on stage for their final performance, pleasing the fans so much that they call for an encore.

Following μ's' victory at Love Live, Graduation Day finally arrives at Otonokizaka. Whilst Nico shows her family around, Honoka and the others work on preparations for the graduation ceremony. Honoka soon comes across Eli reminiscing in the student council room, and gives her thanks to all she has done for everyone. As the opening ceremony gets underway, Honoka presents her commemorative speech, which turns out to be a special song she and the others had prepared for the third years. After the ceremony, Nico assigns Hanayo as the next president for the Idol Research Club, with Maki nominated for vice-president, before the group take a reminiscing tour around the school. Arriving at the rooftop where everything began, Honoka gives a proper sendoff to the name of μ's. Before the girls can get a chance to part ways, Hanayo receives some 'big news', prompting everyone to rush back to the club room.