Investigate Tomb where Bayek Killed The Heron
All Story Quests
All Assassin’s Creed: Origins Guides

To find and rescue Kawit in Gaia’s villa in Children of the Streets in Assassin’s Creed: Origins kill the guard in the courtyard area and pick up the Gaia’s villa cell key:

To find and rescue Kawit kill the guard in the courtyard and pick up the Gaia’s villa cell key.

Go the the back of the courtyard and down the stairs. Go into the cellar and interact with the door.