It's just after the events of Security Breach and the construction team finds something they shouldn't while trying to clear out the underground area. (Fredbear x SpringBonnie, Glamrock Freddy x Glamrock Bonnie. Glamrock Bonnie was always alive in this, btw).
Set before Foxy and Bonnie are replaced, but not by much. The story of Foxy realizing just how human they are as animatronics and after getting thrown out, he learns to show it to the others as well. (Glamor Freddy x Bonnie, Glamor Chica x Roxy eventually).