"Space opera's the same, but they call it le space opera."
It's been a long time since I lived in France, so my sense of what is idiomatic has no doubt grown rusty, but "Théâtre D'opéra" doesn't sound right. The word "Théâtre" doesn't belong in a reference to the place where operas are performed. It's "L'opéra Garnier" and "L'opéra Bastille" in Paris and "L'opéra Nouvel" in Lyon, for example. I'd read "théâtre d'opéra" as more like "operatic theatre" in the sense of a genre (contrasted with, e.g., spoken-word theatre). I could be completely wrong here, but the title feels like a naive machine translation.
"My name is Scroder Cher. I take care of the place while the Master is away."