Tegami Bachi: Letter Bee - Season 2 Episode 9 200 Years of Solitude

200 years ago, Niche and her twin sister were shunned as cursed, and were eventually disposed of. Thrown into a river, with the most precious thing in the world, her sister, split apart from her, she matured all on her own, and has lived together with the Maka ever since. When Niche finally encounters her, she has no recollection of what happened, and instead protects Lag, a "human." Shocked by seeing her sister in such a state, she tries to kill both her sister and the other people. Lag tries to stop her, and shoots a shindan into her with his feelings...