Twoearle

Twoearle is an unknown girl that comes from another world, who claims Sōji Mitsuka to be the only man with the most potential of using Tail Gear, and entrusted him one to fight the monster, by transforming into Tail Red. She also gives Tail Gears to another chosen twintailed girls who has potentials, and oversee them. Twoearle comes from an alternate world and developed the Tail Gear bracelet based off technology that the Ultimaguil intentionally leaked, unaware that she was being manipulated into becoming a savior for the world in order to spread the twin tail attribute across the world so the Ultimaguil could later come and harvest it for sustenance. Becoming Tail Blue thanks to the Tail Gear bracelet she made, Thouars attempted to fight off the invaders but failed as the twin tail attribute completely disappeared from her world as she escaped to the world Soji and Aika lived in and intentionally relinquished her own twin tail attribute and created the Tail Gear that Soji Mitsuka/Tail Red uses to fight the Ultimaguil.