The story tells that Mizuto Irito and Yume Ayai were boyfriend and girlfriend in junior high school. Because of a misunderstanding, they broke up when they graduated. However, when they entered high school, their parents remarried, and the former lovers became siblings. The memories and the situation of living under the same roof made it impossible for them not to pay attention to each other's every move. The original novel was written by Kashiro Sakaisuke and illustrated by Takayaki. It began serialization on KADOKAWA's novel submission website "KAKUYOMU" in 2017 and was officially published in 2018. It has won the "3rd KAKUYOMU Online Novel Competition" Love Comedy Department Grand Prize, "This Light Novel is Amazing! 2020" Library Department New Work 3rd Place and other awards.