I Just Want to Have Pure Love but My Fiancée Forces Me to Become Neptune

[Western fantasy + sword and magic + Mary Sue + no system + give everyone a whole life] Wayne accidentally traveled into a classic Mary Sue novel and became the fiancé of the biggest female villain in the book. When he learned that his fiancée was destined to die, Wayne was determined to change this absurd ending. However, things are not simple - the female villain has become interested in him, and the heroine seems to have some intentions towards him. Faced with these complicated emotional entanglements, Wayne just sneered and thought to himself: laugh to death, here is pure love.