Even though you can’t pick Bunny as a starting character, you can still unlock her early on in the game. Here’s everything you need to unlock Bunny in The First Descendant

Just clear the first zone and the first boss. Screenshot by Dot Esports You can unlock Bunny in The First Descendant by completing her respective subquests. After you reach the second battlefield in Kingston, you receive a subquest called Obtaining Bunny Suit Basic Materials, which has multiple stages.