From 24th to 28th March 2023 (dates may vary by timezone), Tetris 99 will be running a Fire Emblem Engage themed Maximus Cup.
Players who earn 100 event points can redeem a Fire Emblem Engage special theme.
Note: A Nintendo Switch Online subscription is required to play Tetris 99. In certain territories (such as Europe and Japan), there’s currently a free 7-day trial available from the My Nintendo website.
According to the Japanese website, if you missed it, the Fire Emblem Three Houses special theme can also be redeemed with 1 ticket (instead of 30) during the same period.