sssr, the inner voice is the protagonist's (Misaki), as she tells Beherin the story involving her classmate. And yes, her name is Sakuri-san, there's even furigana in the manga indicating the reading, さくり. The name (咲理) actually exists, but the reading is usually Emiri, Eri or Sakiri. If it wasn't for the furigana, I'd probably guess it was Emiri, but the author put furigana indicating this reading.
MinecraftNoob, have no idea. This was a short but a powerful story imo. Hopefully the author will mention whether it kept happening with the other students sometime in another chapter. But my guess is that is stopped happening since the one who started it no longer did it.