Kaito finds himself inside his favorite book, "I Became the Villainess and Rewrote the Ending" — itself an isekai where tomboy Suzuki wakes up as villainess Elara Voss and saves a kingdom. But there's one problem, in the original ending she marries the most boring prince alive!

Kaito wakes up inside her isekai story as Ren Aldric, a mob character so minor he doesn't appear in the novel by name.

Suzuki is already there. She arrived the same day he did, in the body of Elara Voss, and she's running her plan. She thinks she knows the story thanks to playing the otome game over and over. But only Kaito knows the full story — including the ending she's walking toward without knowing it.

He's here to give her a better one.