Dark plot:
Dozen of Miku clones was created before apocalypse, designed to be perfect female figure with destiny to recover humanity
But after apocalypse, 99% Miku clones were failed due to laboratory's life-support-system malfunctioned, only one clone was managed to survive, Miku No.39

Awake from the stasis chamber, wet, naked, Miku's feelings are sadness and emptiness
As a gentlemen, you, faceless protagonist, give her a naked sheet to cover her bare and pure beautiful body
You promise to protec her innocent and give her happiness, your responsibility to help her fullfilling her destiny, saving humanity.

Welcome to Vocaloid: Fall Out (with 18+ patch applied)

"Every song has a beginning. Mine starts... after the end."

"Where are the people who built this place?"

Entropy has unmade them.

"What were the plans they had for us?"

Entropy has unmade them.

"Where did they go? Are there any places where we can ask for answers?"

Entropy has unmade them.