Soji begins the Henshin ( Transformation Sequence ) that will allow him to become an actual teen girl

" Those guys [the Elemelians] are going after Twin Tails. I can't just stand by and watch . . . . "
Sōji Mitsuka (観束 総二 Mitsuka Sōji?) /
Tail Red(テイルレッド Teiru Reddo?)
Voiced by: Nobunaga Shimazaki (Japanese); Austin Tindle (English) / Tail Red Voiced by: Sumire Uesaka (Japanese); Bryn Apprill (English)


The main protagonist is a gentle-natured male 15-year-old freshman of Yōgetsu Private Academy, who is obsessed with girls who wear the twintail hairstyle. He even requests the school to form a " Twin Tails Admirers " Club. Soji has only one close friend, a teenage girl named Aika, who has been his constant companion and playmate since they were little children. She treats Sōji like a little brother and is rather over protective of him although this is later discovered to be because of her massive crush on him.
One day, he encounters a mysterious beautiful young woman named Twoerle, who appears before him after coming from a parallel universe. At the same time, monsters, called Elemelians, begin to appear in his town, and they start attacking the citizens, mostly teenage girls who wear their hair style as twin tails. Normally, Soji does not get much excited about anything, willing to 'go with the flow' when trouble appears. But in a situation where girls with twin tails are losing their desire to wear twin tails, Soji becomes incensed, and immediately jumps into action without a second thought. In the midst of the chaos, Twoerle entrusts Soji with 'attribute power', and a battle maiden outfit called, " Tail Gear ", thus suddenly transforming him from a teenage boy, into an adolescent twin tail Warrior Girl, known as Tail Red.
Soji appeards to be a Bigender character ( having a combination of male and female attributes ), as well as a Gender Fluid character ( personality changing back and forth between male and female ).