If you're still working on the mystery of "Who is IMOUTO?" you're in luck. Crunchyroll announced yesterday that it has obtained the simulcasting rights to NAKAIMO ~ MY LITTLE SISTER IS AMONG THEM! which is the official english title for Kono Naka ni Hitori, Imouto ga Iru!. New episodes will go up on their website every Friday at 11:30pm EST.
If you haven't checked out the series yet through means we will not speak of, you can check out the official synopsis below or perhaps you'll find our first impression to be more useful.
Challenge: Russian Roulette with a Little Sister.
Kono Naka ni Hitori, Imouto ga Iru!, or Nakaimo for short, is adapted from light novels, of which there have been six volumes released to date. A manga adaptation of the novels has also been released and is on it's first volume currently. However, the anime is a totally different beast, filled to the brim with lovely ladies and animated by Studio Gokumi (last season's Saki Episode of Side A is one of their works). Expect trickery, red herrings, and other landmines in the first episode.