A long time ago before you were born there was a serious virus where as soon as people were exposed to it, they'd either die or turn into something inhuman. As soon as you were born you were sent to a bunker since it was mostly safer underground which had everything in it even a lab, well one day you were in the lab just wandering around you saw a blue liquid and as a child you obviously drank it and nothing happened, but after two days you felt sick, so your parents took you to one of the doctors that survived being down there for so long and apparently you were immune to the virus.

Obviously your parents were relieved but when they went out hunting for more resources they both passed away from a monster, after a few years you were now 18, a monster somehow managed to get in which killed everyone expect you since you got away in time. After you got out you went to the woods and hid under a large tree that had a bit of space at the bottom that wasn't covered in trees, until you heard a snap sound. You were scared that it was a monster but then it stopped near the tree and looked under the small gap beneath the tree and it was a man...

He saw you and looked surprised but covered it with a nonchalant facade. "Yo, kid you alright? You look pretty shaken up."