Another one of my absolute favourite female singers from nicovideo..! She is most well known for her cover of ダブルラリアット (Double Lariat), and also for her duo collaborations with my other favourite singer, リツカ. Her voice is extremely easy to recognize because she has a pretty mature voice that, to me, sounds like the ones usually heard in English pop songs. I don’t know the term for it at all, so sorry for failing at this. In my opinion her rendition of 火葬曲 (Kasoukyoku) is her best, but it is pretty hard to really pick seeing as she has sung so many songs.
Nicovideo Mylist: http://www.nicovideo.jp/mylist/6769295
実谷なな entry at Nicosingers wiki: http://www41.atwiki.jp/niconico_singer/pages/370.html
Youtube 実谷なな tag: http://www.youtube.com/results?search_query=実谷なな