Music & Lyrics : Mikito-P
Vocals : Rib / Hatsune Miku
Illustration & Movie : CHRIS
Hopefully I interpreted the song correctly, so here goes, a summary of the song/story, translation of the Sarishinohara short comic done by CHRIS.
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
The catchy line from the song, それでも君が好きだよ (Sore demo kimi ga suki da yo) has a similar ring to Sashihara's song, それでも好きだよ (Sore demo suki da yo). Not to mention the 2nd last line of the song, 刺し殺されてしまっても (Sashikorosarete shimatte mo), the word SASHIKOrosarete is also referring to Sashihara (her nickname is Sashiko) - Info thanks to Youtuber xAkimiya
Also in the PV, you can see the sunflowers everywhere. In Japan, there's Hanakotoba, similar to English's flower language, the sunflower means admiration/to long for something, passionate love, splendor, adoration and 'I only look at you'.「 私の目はあなただけを見つめる」
To celebrate Sarishinohara having 100,000 views, CHRIS drew a short manga and uploaded it to Pixiv, click the pic below for the original link to pixiv (go increase some favourites/views for that awesome illustrator!), read on for the translated version.
Note : In Japan, the 2nd button of a male's school uniform is referred to the button closest to the heart, so usually during graduation or other special events, the girls would ask for the 2nd button and/or the guy would offer the girl his 2nd button.