The Voice of My Unfamiliar Little Sister (見知らぬ妹からの声 Mishiranu Imōto kara no Koe) is the 1st episode of the Kono Naka ni Hitori, Imouto ga Iru! anime series.
Shougo Mikadono, heir to the Mikadono Group, enrolls in Miryuin Private Academy, also having to find his potential wife there. He saves a girl named Konoe Tsuruma from a oncoming truck outside a bakery, and she later shows him to his homeroom class after they briefly share cream puffs at a park. Shogo explains to Konoe that he received a scar on his forehead after an accident as a child. After Konoe is summoned to a student council meeting, Miyabi Kannagi tries to make a move on Shogo, but he backs out of it. Later at night, he receives a birthday cake and an action figure by mail. After seeing a photo of him as a child being kissed by an unknown girl at an amusement park, he receives a phone call from this girl confirming this. The next morning, he ponders if the girl who chooses to marry will end up being his little sister.