Collect 7 Bt21 Characters. Bt21 is the First Project of Line Friends Creators. Meet 7 Different Charming Characters Created by Bts Members. Prince Tata From Planet Bt, Who Had Been Traveling With Van, Crashed on Earth. In Order to Spread Love, Tata Decides to Become Star. Finally, They Have Met Six Fascinating Members: Koya, Rj, Shooky, Mang, Chimmy, and Cooky to Make ‘bt21’, and They Are Dreaming of Becoming the Most Famous Star in the Universe, the Universtar! Will Bt21 Become Universtar, and Spread Love Around?