A dark, depressed, "emo" variant of Himekaidou Hatate of Touhou. Created and popularized by rui (hershe), alongside similarly dark variations of Shameimaru Aya, Inubashiri Momiji, Murasa Minamitsu, and Kawashiro Nitori.
In his story, Hatate is a schoolgirl in love with Aya. However, Aya verbally and physically bullies Hatate, who tolerates and may even be masochistically turned on by the abuse. Momiji is sympathetic to her, but because she's a lackey to Aya, she doesn't involve herself. Nitori appears to be Hatate's online friend. Murasa is Aya's rival.
Black hair is a common Hata-tan trait, but isn't required. Images may also include some combination of bags under the eyes, bullying, scars, marks around the neck from choking, a hikikomori or obsessive, yandere character, often with Aya as the focus, or identification as Hata-tan by the artist.