Aine and Mio hold a concert for the reveal of their Diamond Dresses. As part of that concert, the members of Best Friends! want to thank their fans for their support. Mio gets a surprise when her father shows up to attend the concert, and a secret about the Diamond Dresses is revealed.

The girls finally arrive in the Sorbette Kingdom, but find they are banned from entering by the country's military on Alicia's orders. However Alicia's younger brother Charles comes to the rescue and allows them entry. Hibiki speaks with Alicia and attempts to convince her to reform I Believe but Alicia refuses. While wondering what to do next, Charles asks the idols about Aikatsu as no one in the kingdom has heard of it. Aine and Mio decide to hold a concert to introduce the people of the Sorbette Kingdom to Aikatsu.