A college student died and got reincarnated into the world of a manga he once loved. Not as the main protagonist or as a side character, but as the antagonist? Would he be able to change his future?

Y/n is from the Sengoku era and was reborn to the Taisho era were tanjiro is now. Y/n was abandoned by her own parents and left her to starve in the cold. Then someone came along and it's was a strong demon Slayer that took her in. It was the one and only Yoriichi tsugikuni he didn't want to leave a child to starve in the cold so he took her in and took care of her. He didn't want to see her die in the future so he taught her how to use the sword and combat skills but she was able to learn them quickly. She knows how to use the sun breathing and the other main breathing styles too. The sengoku era hashira know who Y/n is and was amazed of how qui ck she learned. Y/n was there when Yoriichi was fighting Muzan and she was only 13 year old. Y/n died by a illness. When Y/n realized that she was reborn she was upset that Yoriichi wasn't with her anymore. But along the path she meets a boy that is quite familiar and she realized who the boy is, he was part of the kamado family. (She knows a kamado family because she used to visit them a lot.) That was not the only thing she realized he had Yoriichi earrings meaning that he is Yoriichi tsugikuni successor.