I think the opera matches many of the storys of FFVI. Loosing your loved ones, and loss in general, is a component to every chracters being. Setzer lost Daryl to mystery, Sabin and Edgar lost each other and are reunited. Locke lost his love to death, twice! Celes looses everything, only to litterally take on the world to reclaim it. Terra is lost. Gau lost his father. Gau's father lost his mind. GoGo lost a traditional battle menu, but gained so much in return.

Everybody deals with loss in the game. Different types, different outcomes, and different ways.