The film begins by taking us back to Honoka's childhood, where she is determined to jump over a puddle left by a heavy downpour. Cheerfully supporting her is Kotori, while Umi stands on the sidelines offering encouragement. Despite numerous failed attempts and Kotori suggesting that Honoka give up and head home, our tenacious protagonist ultimately succeeds, triumphantly leaping over the puddle.
Fast forward to the events following the second season, μ's learns that Love Live! is gearing up for a third competition set to take place at the iconic Tokyo Dome. The girls realize that in order to achieve this grand ambition, they must significantly enhance their publicity to ensure a sold-out performance. With the goal of expanding the appeal of school idols to a wider audience, μ's decides to embark on an exciting journey to the United States, where a well-known TV agency has invited them to participate in a special program. Initially contemplating disbandment, the girls choose to perform, fueled by their commitment to support Love Live! and secure their legacy as school idols until the month's end.
As μ's gears up for their live show and practices in the bustling streets of New York City, they also take the opportunity to enjoy some tourist attractions. This montage culminates with the insert song "Hello, Hoshi o Kazoete" (Hello,星を数えて), evoking nostalgia for their carefree escapades. However, Honoka’s solitary moment quickly shifts when she gets separated from her friends, only to discover a solo Japanese female singer captivating the streets with her enchanting rendition of "As Time Goes By" (Japanese) / "Stars, Come to me!" (International). Drawn to her mesmerizing performance, Honoka is compelled to engage the singer in conversation, uncovering their shared experience of creating music with close companions. The singer's haunting story, filled with heartbreak and loss, reveals her loneliness in New York after facing multiple farewells. That night, as Honoka walks back to her hotel, she reflects deeply on the singer's poignant question: > “What's most important is, whose sake do you sing for?” The first act of the film concludes with μ's delivering a spirited performance of "Angelic Angel" in the bustling heart of New York—Times Square and Central Park.
As μ's' fame skyrockets across Japan, the group is inundated with throngs of enthusiastic fans, transforming Akihabara into a vibrant tapestry of μ's memorabilia and advertisements. Now international icons, the girls resort to clever disguises to navigate their newfound celebrity status. Accompanied by the hauntingly beautiful "?← Heartbeat" (Hate na Heartbeat), they confront the overwhelming nature of their fame and the mounting pressures of fans pleading for the group to continue indefinitely. This relentless admiration begins to erode their resolve as they grapple with the heavy consequence of their impending disbandment.
Struggling with self-doubt, Honoka receives an unexpected visit from Principal Minami, who offers a compassionate ear and words of encouragement, urging the girls to reconsider their decision. The principal's sentiments are mirrored by Tsubasa, who engages in a midnight dialogue with A-Rise, broaching the topic of potentially extending μ's journey as a professional music group.
As Honoka wanders the rain-soaked streets, burdened by her responsibilities, she is captivated by a mysterious voice singing a haunting melody. Recognizing this singer from their previous encounter, Honoka feels an intense gratitude and impulsively brings the stranger to her home. However, just as they are about to share a heartfelt moment, the singer departs suddenly, leaving Honoka with an overwhelming sense of loss.
In a moment of intense introspection, the singer reappears, posing the question that has been resonating within Honoka: what is the answer to her most profound desire? Standing before a picturesque lake adorned with blooming flowers, the singer challenges Honoka to leap across the water. Though apprehensive, Honoka takes the leap, and as she soars through the air, she rekindles her passion for being a school idol.
Meanwhile, Eli delivers an important message from the third-year students, affirming their unanimous decision to conclude their idol activities. The weight of this decision looms heavy over Honoka as she contemplates the future of μ's amidst the boundary-less sky ahead.
As dawn breaks, Honoka returns to their familiar rooftop gathering spot, where the group's determination converges. With steadfast resolve, she unveils her ambitious plan: a grand concert extravaganza aimed at uniting all school idol groups as a final homage to the craft. Her proposal resonates with Tsubasa, who wholeheartedly supports the initiative at UTX High School.
Undeterred by the lukewarm replies from the majority of school idols, Honoka and her friends embark on a nationwide journey, utilizing Maki's financial support for train tickets. Traveling in groups of three, they set out to persuade their peers to join this momentous occasion. The monumental gathering culminates in Akiba, setting the stage for an unforgettable school idol festival.
Behind the scenes, Kotori and Anju collaborate to design the costumes, while Maki and Tsubasa work tirelessly to compose a captivating song. As the eve of the event approaches, Honoka shocks everyone by announcing that μ's' disbandment is on the horizon, sending ripples of disbelief throughout the group.
Finally, the much-anticipated day arrives as μ's makes their way to Akiba. Amid the hustle, Eli initiates the festivities with a spontaneous race, as μ's takes its first steps towards the stage. Honoka's attention is momentarily captured by a drifting petal, evoking memories of ethereal blooms on a distant hill. Seizing that moment, she allows her spirit to take flight, showcasing graceful pirouettes and spins along her path.
Upon reaching the stage, μ's is met with an awe-inspiring sight—every school idol group has come together, adorning costumes that reflect their unique styles. A sea of eager fans creates a clear path to the stage, launching the festival with the performance of "Sunny Day Song," now recognized as a unifying anthem for all school idols.
As a new academic year begins at Otonokizaka High School, two dedicated members of the esteemed Idol Research Club, Yukiho and Alisa, step forward to honor the legacy of μ's. The duo delivers an invigorating welcome speech for the freshmen, sharing stories about how μ's saved their school and the thrilling nature of their final performance. This critical moment serves as a nostalgic reminder of the group's extraordinary journey.
The scene seamlessly transitions into a heartfelt flashback, capturing the backstage emotions before μ's last idol performance. Passion and excitement fill the air as the group prepares for their ultimate show.
As the curtain rises on their final act at the legendary Akiba Dome, the movie culminates in an emotional performance of "Bokutachi wa Hitotsu no Hikari," a heartfelt anthem marking the commencement of μ's farewell show. This stirring finale leaves audiences yearning to witness the group’s unforgettable last chapter.
