Reincarnated Inside My Own Novel ?

Will was a famous novelist of him time. As such he wrote realistic novels (ie that had deaths, betrayal, Mc also losing etc etc). In his most recent novel , 3 out of 4 MCs were killed by him. But fate has something else in store for him. He has been reincarnated in his own novel. But that's not the end. His mission ? To save the 3 MCs which were killed in his novel, and if he fails it leads to his death. Whats even worse is that he has been reincarnated as a mob character. How will he save the 3 MCs and in turn himself ? Let's find out