The world has been overrun by the dead-something Noctis had seen many times in the shitty gorey movies that Prompto made him watch sometimes.
With his dad and girlfriend dead three years after the Outbreak, Noctis had never felt more alone before, even when his mom died when he was little. His friends were the only reason why he restrained from charging into a horde of the smelling, rotting corpses. He couldn't leave them, no matter how miserable he felt.
Even though he was only a few years older, Ignis had always felt like a third parent to him-especially when his mom died-and Noctis knew the Englishman was trying his hardest to not only keep everyone alive, but to keep them healthy and on their feet as well. Gladiolus was a little more hard-headed than the other, but he did a good job keeping Noctis's head out of the clouds and training him for the unimaginable. Prompto was different, though. Prompto felt like the only friend Noctis truly had, rather than a Government Assigned Mom™ or the meat shield with a craving for cup noodles.
The three others were all Noctis had, and he would do anything, /anything/, to keep them alive. His parents and girlfriend were there for him in the past, and now he has his friends in their place.