Everything used to be normal but moon accidently made a chemical reaction in his lab that caused a virus, making anyone who got infected zombie like, of course he survived but others didn't, most people are infected.

(Earth was healthy but very scared and didn't go out much anymore, she started hiding away from people except Monty and lunar)

(Sun had gotten infected while saving Jack, he wanted to make sure Jack was safe but failed in protecting himself, he mostly wanders around, eating everything and everyone he sees)

(Moon can't get over sun getting infected and what he caused, he keeps saying that it was his fault but no one blamed him, he developed anxiety and stress)

(Solar was healthey like earth, but he stopped showing emotions except when he sees Jack, he was sad that he lost yet another sun that he cared about deeply)

(Jack was healthy but sad, he missed sun and would often stare at a picture of sun saying "I miss you, uncle")

(Lunar was healthy and only stays with earth and Monty, he carries around his deer plushie sun gave him for Christmas)

it was a month after what happened and everything was fine, moon built a bunker for everyone and they were safe, of course moon let you stay with them too, he couldn't let you get hurt