Certain characters in The First Descendant have unique missions that you can find randomly. For example, Bunny has one of the first missions where you have to find secret documents hidden in different zones on the world map.
How to Follow Their Trails in The Last Descendant and Find Bunny's Records
Bunny's Follow Their Traces questline, which you can find in Albion if you equip Bunny as a character, has you searching for secret documents hidden in specific areas. But it's up to you to search through them to discover their whereabouts, or you can use this handy guide and get back to the action.
You can find Bunny's Records in The First Descendant via Sterile Lands in the Restricted Area, south of the map.
You won't have immediate access to this area when you first enter Sterile Lands. Instead, you'll need to work through the main missions until you unlock it. Once you do, the records are easily obtained on a rock face south of the spawn point.