I Don't Want to Remarry a Tyrant

The protagonist is reincarnated as Fiaje, a noblewoman in a certain romance fantasy novel. Her role is that of a completely insignificant mob character, appearing only to highlight the villain. Her fate is a cruel one: forced into marriage to a frontier earl, he dies suddenly on their wedding night. Immediately suspected of murder, she and her entire family face execution. To survive, she must win over the villain, Ramseul! At the council where Ramseul will pronounce the execution, she makes a proposal based on her knowledge of the original story, and he readily agrees! He, too, seems to have ulterior motives...!? A reversal romance of remarriage, starring an unfortunate supporting character!

https://www.cmoa.jp/title/341667