Pet by Aiden E. Messer

In the aftermath of an apocalyptic event that sets the world ablaze, Caleb and Nivitha find themselves thrown into a harsh, unforgiving new reality. They must face their fears, adapt to the dangers of their environment, and decide whether to trust others or isolate themselves. 

Caleb, social by nature, quickly makes a new group of friends among the survivors.

Nivitha, determined to protect her younger sister Asha, guards herself against the remaining humans, regarding them as potential threats.

They both soon learn just how cruel this new world can be. Between murder, torture and hunger, uncertainty is the only constant.