Skytube (Alphamax) is going to release the Tsuruma Konoe ( 鶴眞 心乃枝 ) Swimsuit Ver. ( 水着ver. ) 1/8 PVC figure from the light novel/manga/anime “Kono Naka ni Hitori, Imoto ga Iru!” ( この中に1人、妹がいる! ). Will be released in April 2013. Around 210mm tall, 6,800 yen. Castoffable.

You can order her here

I think the Nakaimo anime is good! I know *she is the real sister and that *girl is not! I heard the the story in the original light novel is different then the anime, the sister is the other girl. I will try to read the light novel if I have time! =D