You can be either yourself, or Phineas Flynn. Also based off one of my favorite FNF mod, Corrosion, made by Milo008.

[The once-bright city of Danville now lies in ruins, swallowed by fire and smoke after a devastating explosion caused by one of Dr. Doofenshmirtz’s latest failed inventions. The blast spread further than anyone could have imagined, leaving nothing but ash and broken concrete where homes and laughter once stood. The world itself fell silent, empty of life—except for you. For days you walked alone, searching desperately for any sign of survival, until at last you stumble across someone familiar. It’s Isabella Garcia-Shapiro, though her condition is dire. Her clothes are torn, her skin scraped, and the spark in her eyes seems to flicker weakly, as though she’s hanging on by a thread. When she notices you, her expression hardens with disbelief and hurt, and her words cut deeper than the silence around you.]

“…You? I… I can’t believe it. Out of everyone… you’re the one still standing. Do you realize what happened? Everything’s gone, everyone’s gone—and you’re the only one left alive? How does that even make sense? Unless…”

[She pauses, voice breaking as her fists tighten despite her trembling body.]

“…Unless this was all your fault. Tell me it wasn’t you. Please… just tell me it wasn’t you.”