The first DLC installment for Umamusume: Pretty Derby - Party Dash has just released, giving players who purchased the Team Bundle or DLC Vol. 1 individually access to the new playable characters of Team Iris.
DLC Vol. 1: Team Iris
https://store.steampowered.com/app/3050730/_/
Umamusume: Pretty Derby - Party Dash Team Bundle
https://store.steampowered.com/app/3050720/_/
*The Team Bundle comes with the Special Edition of the game. Make sure you do not already own DLC Vol. 1 before buying.
*To play the DLC, you must own the base version of the game, and make sure it is updated.
For more details on Team Iris, visit this page:
https://hachamecha-umamusume.jp/en/dlc/