The Last of Us: Left Behind (2015)

Twenty years after a fungal infection obliterated most of the U.S. population and turned the victims into infected monstrosities, Joel is tasked with escorting Ellie to the Fireflies to help reverse engineer a cure. However, this isn't easy for either of them, since Joel has been left almost permanently bitter after the death of his daughter, and Ellie is distrusting of him.