One-line summary: She awakens supernatural powers and transmigrates to another world. By transmigrating into a book, she saves a world on the brink of destruction. (No splitting into multiple personalities.)
Full summary: She and her younger brother have struggled to survive in the apocalypse for five years. Just as she is about to give up, she gains the power to transmigrate into books and bring supplies back from other worlds.
She thinks she might finally be able to keep herself and her brother alive, and even save this world along the way.
But the task of saving the world should be handed over to the state. Earning huge amounts of merit every time she transmigrates into a book is hard enough.
