Following their summer vacation, Futaro Uesugi, Yoshitsugu Matsuoka, and the Nakano quintuplets—Ichika Nakano, Kana Hanazawa; Nino Nakano, Ayana Taketatsu; Miku Nakano, Miku Ito; Yotsuba Nakano, Ayane Sakura; and Itsuki Nakano, Inori Minase—now enter their final year of high school and gear up for the school festival. The mood is hopeful and busy as each sister pursues her own path, while Futaro’s carefully planned confession sits at the center of the event: to reveal which sister he truly loves, he asks them to wait until the festival ends.
On the festival’s second day, Ichika’s onstage work reveals distress among her sisters when one of them collapses. She rushes to the hospital and finds Futaro and Nino visiting. Later, Ichika and Futaro share a quiet moment outdoors, and she kisses him in a park, a moment that tugs at the delicate balance of their promises and feelings.
Meanwhile, Nino faces her own family drama. She expects her father, Maruo, to appear at the school, but he is not where she looks. Futaro comes forward with a video that confirms her father’s attendance, and the pair visit him in the hospital, where Nino quietly cooks a pancake for him. After this heartfelt reunion, Nino kisses Futaro and thanks her father for choosing him as the quintuplets’ tutor, a gesture that deepens the bond between their tangled family and school life.
On the first day of the festival, Miku accompanies Futaro as they approach the boys’ takoyaki stand and she promises that the group backing the pancake stand will enjoy their food. A dramatic turn comes when the takoyaki stand catches fire, forcing the group to respond to the emergency while the festival continues around them. The incident becomes a catalyst for additional tension and concern among the friends.
The third day brings a rooftop encounter. Miku invites Futaro up and they encounter two classmates arguing about the takoyaki incident. After admonishing the quarrel, Miku confronts Futaro, driven by jealousy from his rumored meeting with another girl the day prior, and she kisses him in a moment of intense emotion.
Yotsuba, ever the workhorse, is found overburdened by her club commitments. She collapses on the festival’s second day and ends up in a hospital, where Futaro explains that some of the students she has helped offered their support during her absence. On the third day, she steals another moment with Futaro—kissing him while he rests—before the emotional pace of the festival continues to rise.
Itsuki’s arc unfolds as she studies during the festival’s opening day, where her teacher Mudō reveals a history with her mother. The next day brings a painful revelation: Mudō is the quintuplets’ biological father, a discovery that leaves Itsuki furious about the past decisions that shaped her family. On the festival’s third day, Futaro visits Itsuki at home, encourages her to pursue her dream of becoming a teacher, and reinforces the belief that she can carve her own path.
Tensions swirl as Maruo, Futaro’s grandfather Isanari Uesugi, and Miku (disguised as Itsuki) confront Mudō. Itsuki confronts Mudō, declaring that he is not suitable to be the quintuplets’ father after failing to see through the disguise and recognizing the way past choices have affected their lives.
As the festival draws to a close, the quintuplets urge Futaro to move toward one of them with his confession. He seeks out Yotsuba and declares his love, but she initially rejects him, seeing herself as unworthy of him. Her heart remembers their first meeting and the promise they made to each other. In a turning moment, Futaro catches up to her, persuades her, and listens as she reveals her true feelings. Yotsuba decides to put her sisters’ happiness first before dating Futaro, a choice that leads them to reconciliation. Once they overcome their differences, the couple begins dating.
Time passes, and life afterward moves forward to a five-year leap. Nino and Miku have opened a cafe together, Ichika pursues acting, Itsuki teaches, and Yotsuba stands close to marriage. As a wedding gift, Yotsuba’s ears are pierced to wear her mother’s earrings, symbolizing the continuity of family and love. On the wedding day, the quintuplets stage one final game for Futaro: instead of him guessing which sister will marry him, he identifies each sister one by one, demonstrating the deep trust and closeness they’ve built over the years. The wedding marks a new chapter for the by-then-close-knit sisters, and they briefly discuss the best country for the newlyweds’ honeymoon, a light note to end a story of growth, sacrifice, and enduring affection.
