Also, is Sakakibara a common Japanese surname.
I just learnt about the Kobe murders and wonder if there may be something intentional in the use of that name here or just coincidence.
Not very common but not too uncommon (shit answer, I know)
But, I am going to take a wild guess and say
yes this might be where Sel got the inspiration. Kanji for surname Sakakibara is most likely 榊原 due to its samurai origin. However, in the case of Kobe murder, the murderer wrote his alias Sakakibara intentionally as 酒鬼薔薇 in a full blown chuunibyou manner. A word-by-word direct translation to that alias is
alcoholic rose (or rose of alcoholic depending on how poetic you want to be), and this alone fits Sara’s character all too goddamn well even before thinking about whether this inspiration extends to Shota’s death or not.
Edit: ok, the most word by word translate would actually be like “sake-oni-bara”, thus “liquor-ghost/demon-rose”. I in fact took the liberty of interpreting the sake-oni part as alcoholic.