Kono Naka ni Hitori, Imouto ga Iru!: Ani, Imouto, Koibito

Ani, Imouto, Koibito (Brother, Little Sister, Lover) is the unaired thirteenth episode of the TV anime Kono Naka ni Hitori, Imouto ga Iru!, released on home video.

The series follows Shougo Mikadono, the heir to the powerful Mikadono Group, who transfers to an elite academy after his father's death. Before long he receives a mysterious message from someone claiming to be his younger sister – a half-sister he never knew existed. The problem is that she does not reveal who she is, and several girls at the academy could be the one. If Shougo wants to inherit the family business, he must also find a suitable bride, which puts him in an awkward position: the girl he falls for might turn out to be his own sister.

The series mixes harem romantic comedy with mystery and fanservice, as Shougo tries to work out which of the girls around him is his sister while their affections for him grow ever more complicated. As the title suggests, this bonus episode plays on the tangled lines between brother, sister and lover that drive the whole story.