Masamune Izumi is a high school student who professionally writes light novels. Sagiri Izumi is a shut-in who never leaves her room. One year ago, they became siblings when their parents married one another. The closed off room opens up, and the sibling story continues. Masamune and Sagiri encounter more obstacles, as well as new beginnings. As they take steps toward their dreams together, they learn a little more about each other.