MK doesn't pay attention to legends, so he wouldn't understand the legend of the Opera.
But of course, Mei knew the legend since she found the story in Tang's library. So she would've told him the legend of Macaque (the Phantom)... who was a shadow performer and a musician... Then she told him about his relationship with Wukong and how they got separated. Though no one knew what happened to Macaque or that Macaque still lived in the theatre.
30 июл 2023