Mio, Becoming the Hero

Mio starts getting pumped up for she is trying to design a Best Friends Rare dress for Pure Palette. When Mio reaches a wall in designing, Aine invites Mio on a mystery tour planned by Aine herself. Walking along the lands of the forest, they reach the place known as "Hero's Bridge". And to Aine, this bridge that was a part of her childhood memories means?