The 2nd PriPara film, unlike the first this shown in stereoscopic 3D.

Listless geek Mizuto Irido and introverted nerd Yume Ayai seemed like a match made in heaven, connected by their mutual love for literature. Unfortunately, their differences gradually grew, and they separated just after their middle school graduation. But, as if by divine comedy, the two find themselves reunited as step-siblings. A rivalry begins to brew between the former couple, both unwilling to acknowledge the other as the older sibling. In an attempt to "solve" this issue, Mizuto and Yume agree upon a rule: whoever crosses the boundaries of siblinghood norms loses, and the winner will not only be called the older sibling, but also get to make a request. However, now that they live under the same roof, the lingering memories they share start to influence their actions—possibly rekindling the feelings that may not have been fully extinguished in the first place.

Tooru Kirishima's notoriety is spread far and wide in the underworld. He is most commonly known as "The Demon of Sakuragi"—a man who is not afraid to resort to violence if deemed necessary. After almost jeopardizing a peace treaty, his boss tasks him with the most difficult job he has ever had: taking care of seven-year-old Yaeka Sakuragi—the boss' precious daughter—so that Tooru understands what it means to be responsible for another life. At first, the two do not seem to meet eye to eye, as Tooru has no clue on how to communicate with Yaeka, and the young girl is not used to expressing her emotions. However, as time goes on, they come to understand each other despite their differences. The fearsome right-hand man of a yakuza boss and the child he must protect are about to learn that family is not always bound by blood.

These are witches who defend everyone's smiles and fight enemies through the healing power of music. These witches, opposite of those in the defense fleet, are idols known as the Music Squadron.