Square Enix has announced that the 'Temporal Battle Arena' free DLC for I am Setsuna is set to launch on the 13th of April as part of a downloadable patch.
This DLC allows you to take part in battles against other players by downloading data of their AI parties. You can also upload your own data for others to take on. This DLC can only be accessed after you have beaten the game's story. The winning team will be awarded items and Spritnites corresponding to the ones your opponents had equipped.
I am Setsuna is available on PS4, PC and Switch, however, this DLC is available exclusively for the Switch version.