Claiming Ex Astris crossover attire:

Starting January 27, go to the dedicated page for the crossover event and log in there to obtain eligibility for unlocking access to the attire reward. After that, purchase and log into the game using the same account and the attire will automatically become accessible.

Claiming Arknights crossover furniture:

Starting January 27, you can check event reward details on the dedicated event page. After the launch of Ex Astris, go to the said page and fill in the required information following instructions. Once done, you'll be able to claim the crossover furniture in Arknights.

For details on event rules and time, please visit the event page: