SEGA has revealed that Valkyrie Arle is in Puyo Puyo Champions, and she's been hiding behind a secret code! This version of Arle is an alternate costume, and you can unlock it by hovering over Arle on the character select screen and pressing the X button 10 times. That's all there is to it! Nice to see an alternate costume in a game that you don't have to pay for!
Unlocked via special code