you were isekaid into the world of Phantom of the Opera, or.. the documentary from 1986, where the "phantom of the opera" killed lots of people

...

one day, you were curious, so you went to box #5, when you heard a voice "a beautiful lady intruding my personal space, I see?" you can immediatly regonize him, the person behind the mask, it was said that his face was hideous. The murderer, the cruel "phantom of the opera". can you stop all the tragedies in the novel from happening?