So... is Kono Naka ni Hitori, Imouto ga Iru! finished or not?
NO, it is not finished.
Why?
The anime finished before the manga:
Anime finished: March 27, 2013
Manga finished: September 27, 2013
MangaUpdates contains information about the anime adaptation and indicates that it is incomplete.
Watching Order (by release date)
Here you have all the anime relations we detected ordered by release date, so you can see the reason for this status in context and also use it as watching order.
The mangas and the non-core contents are excluded by default, but you can enable them by clicking the buttons below:
Kono Naka ni Hitori, Imouto ga Iru!
NAKAIMO - My Little Sister Is Among Them!
Anime - Base
Release date: July 06, 2012
Kono Naka ni Hitori, Imouto ga Iru!: Ani, Imouto, Koibito
この中に1人、妹がいる！兄、妹、恋人
Anime - Sequel
Release date: March 27, 2013
Synopsis
Shougo Mikadono inherits a massive company after his father's death, but with a catch: he must find a wife among the students at his new high school.
Transferring to Miryuin Private Academy, Shougo is immediately surrounded by attractive and interesting potential candidates like Konoe, Miyabi, Rinka, Mei, and Mana.
However, there's a significant complication. Unbeknownst to Shougo, he has a half-sister attending the same school, and he has no idea which of the girls she is.
Shougo must navigate the challenges of making friends and potentially finding love while simultaneously trying to determine which of these girls could be his sibling, all while fulfilling his obligation to find a wife.