Gonna Be the Twin-Tail!! - S01

Souji Mitsuka, a first-year high school student, is utterly devoted to twintails, believing they represent the pinnacle of human beauty. His obsession leads him to spend his days rating girls' hairstyles and even founding a club dedicated to them. But when aliens invade Earth, intent on stealing the world's twintails, Souji's passion takes an unexpected turn. A mysterious woman named Twoearle recruits him to fight back-by transforming into the twin-tailed warrior Tail Red. Now, Souji must battle Ultimegil, an alien force bent on conquering Earth and draining humanity's "attribute power." Teaming up with Aika Tsube and Erina Shindou, fellow fighters who share his twin-tailed dedication, Souji sets out to protect the hairstyle he loves from the invaders threatening to take it all away.