Bleach: Fade to Black, I Call Your Name

In the Soul Society, Soul Reaper scientist Mayuri Kurotsuchi is attacked in his laboratory by a pair of mysterious siblings wielding a scythe that erases his memories. In a frightened panic, Kurotsuchi damages one of his machines, causing a massive spirit energy explosion that covers much of Soul Society, killing or freezing many Soul Reapers. Rukia Kuchiki is the next to be attacked by the siblings, erasing her memories and those of everybody that has memories of her, and is carried away to Soul Society's Rukon District by the siblings. Read more on Wikipedia.