Reincarnated as a side character

"I'm gonna show you that a side character can be the main character too."–Herabella Venturi
"I beg your pardon?"
“You want me to what?!” I asked aloud what a God had said to me. Is he serious right now? “You want me to save… the villainess?”
"Over and over again? Do you want me to repeat? Save Princess Melusine Ondine, try not to let her die. ” I slapped his forehead and held him on his shoulder.
“Look here God… whoever you are. What you are requesting of me is very impossible to happen. ” Where I said to him.
“Well that’s why-
“Do you want to break the flow of the story? We are in a novel, a very famous book. You want to make readers angry? You want the story to be boring? ”
He sighed and sighed. "She's been through a lot, she didn't deserve death."
I just calmed myself first. Why was I here again? Ah yes, some random God reincarnated me as a side character to save a villain.