Mitsuka Souji, enamored with twin tails, gains powers from Twoearle to defeat the Ultimaguil. Alongside friends Erina and Aika, he battles the enemy leader while navigating romantic feelings.

"Gonna Be The Twin-Tails!!" is about Mitsuka Souji, a boy who's in love with twin tails. He is soon approached by Twoearle, who grants him the power to defeat the Ultimaguil with his love for twin tails. Him and his two other friends, Erina and Aika, will help Twoearle defeat the Ultimaguil and their leader, while love unfolds between the characters.