Sarishinohara is a play on words and it might be referring to Sashihara Rino, a member of HKT48, former member of AKB48. It's a story about a guy in love with an idol but unable to continue loving her because of her career.
On the other side of the story, looking at Sashihara Rino, her alleged boyfriend (named Ton-chan) sent Sashihara's pictures & stories of their relationship to a gossip magazine, and thanks to that, Sashihara was exiled from AKB48 as they have a strict policy on no relationships for the members, so she entered HKT48. I'm sure fans of AKB48 knows how popular Sashihara was, she was placed 4th in the AKB elections.
And so, this song, Sarishinohara, written by Mikito-P, talks about the story from the boyfriend's perspective. There were some speculation as to whether Mikito-P is Ton-chan or not, but I'm inclined to believe that he's not, just my 2 cents as a vocaloid fan perhaps XD
Reprint from NND: www.nicovideo.jp/watch/sm22626672
Voice: りぶ (Rib)
His user on NND: www.nicovideo.jp/user/16133388
His mylist: www.nicovideo.jp/mylist/19160554
His Twitter: @singing_rib
Music/Lyrics: みきとP (MikitoP)
Vocaloid version feat.初音ミク: www.nicovideo.jp/watch/sm22626781
His user on NND: www.nicovideo.jp/user/276638
His mylist: www.nicovideo.jp/mylist/19099704
His Twitter: @mikito_p_