You're The One Who Sent Me The Dark History?

As Iana grows used to life in the world she's been reincarnated into, a young man comes to visit—her childhood friend Yomi, back from studying abroad. When Iana remembers Yomi, a character she created, she is left aghast. His role in the novel is to kill Konoha. If he acts according to the story, it will lead to Iana's death. Iana tries to convince Yomi to stop, but it only makes things worse.