In conclusion to his serialized work "Resonance," mangaka Chikara Nagai plans to kill off Lin, a crucial character, in a surprising twist according to popular opinion. After receiving negative feedback from his editor during a session, Nagai struggles with insomnia while drawing the final panels of his manga. While dozing off, he sees Lin escaping after stealing the page where he dies. Before he can comprehend anything, Nagai is transported into the world of his own creation and finds himself in the midst of a fight scene between Satoko Miura and "The Masque." Unable to differentiate reality from fantasy, Nagai collaborates with Satoko to search for an alternate ending to the manga so that he can escape and return to the real world.
Opus was Satoshi Kons last manga before he debuted in the anime industry through Perfect Blue. The manga had been axed due to the cancellation of its publishing magazine. A missing end chapter to Opus was found after Kons death.