Soji Mitsuka loves the twin-tail hairstyle. Following his first day of high school, he and his childhood friend Aika Tsube are enilisted by a mysterious woman named Twoearle to fight an evil force that threatens twin-tails worldwide!

Student council responsibilities, school work, and Twin Tails activities are taking their toll on Erina, and when her mother pushes her to straighten up, Erina pushes back. When Mikoto is unavailable, Soji must secretly escort Erina on a shopping trip.