 In March 2008, to celebrate its 40th anniversary, "Shōjo Comic" posted free chapters of "Boku wa Imōto ni Koi o Suru" on its website, along with a new side-story.A spin-off series, , began serialization in "Shōjo Comic" simultaneously in 2005.Focusing on Yori's upperclassmen Takuma Kakinouchi and his childhood sweetheart Mayu Taneda, the series ran until mid-2008.