Open the apartment door to another world!? Sara, an ordinary college student, opens her home door as usual, without a single doubt in her mind. However, what awaited her wasn't her familiar daily life, but a desolate riverbank in an "other world" where never-before-seen monsters roam. All Sara has left is a mysterious notebook titled "Isekai Manual." Learning skills from the manual, Sara's otherworld life begins as she starts fires and tames monsters.