Question: What is the genre of music that the nine member group containing Nayeon, Jeongyeon, Momo, Sana, Jihyo, Mina, Dahyun, Chaeyoung, and Tzuyu called?
Sentence (from "Twice (band)"): The group debuted on October 20, 2015 with the extended play (EP) "The Story Begins".
Relevant evidence: No