Days with My Stepsister (義妹生活) is a Japanese mixed-media project created by Ghost Mikawa. It started with a YouTube channel created in April 2020, with its first video uploaded on May 1, 2020. A light novel series is written by Ghost Mikawa and illustrated by Hiten. The series began publication by Media Factory under their MF Bunko J imprint in January 2021. A manga adaptation by Yumika Kanade began serialization online in Kadokawa Shoten's Shōnen Ace Plus in July 2021. An anime television series adaptation produced by Studio Deen aired from July to September 2024.
Premise
After his father's remarriage, Yūta Asamura finds himself getting a new stepsister, Saki Ayase, who happens to be the hottest girl in his grade, and living together with her. Having learned the important values about man-woman relationships, seen through their parents as they carry the scars of their parents’ troubled divorces, and in order to not cause discord in the family, Yūta and Saki promise to keep a reasonable distance from each other, not to be too close or too opposing. Saki, who is longing for affection from her family and worked in solitude for their sake, does not know how to depend on others, while Yūta is bewildered at how to properly connect to Saki as his younger sister. Feeling somewhat similar, the two of them gradually feel comfortable living together.