Title: Angel Sanctuary (Tenshi Kinryouku)
Author: Kaori Yuki
Date: 1994-2000 (original serialization), 1995-2001 (graphic novels)
Media: 20 volumes of manga/graphic novels, 3 episode anime adaptation, miscellaneous drama CDs
Availability: Manga fully translated by Viz media, anime translated by Central Park Media and Media Blasters.
Brief summary: Setsuna Mudou already knows he leads a cursed life—his parents hate him, strange events seem to happen all around him, and the only good thing in his life is also his greatest torment: he’s deeply, desperately in love with his younger sister, Sara. Little does he know, his soul is holding a secret, and the forces of Heaven and Hell are suddenly coalescing around him, eager to return to a war that started thousands of years ago.
Warnings: Think of every possible warning you could ever think of, and it still might not cover everything in this series. But, ah, to start: incest, blasphemy, character death, violence, torture, genocide, child abuse, cannibalism, drug use, sexual abuse, mind control, manipulation, betrayal, reincarnation, identity issues, abortion…
Other Notes: supernatural, drama, religious themes, apocalypse, angels and demons, epic story, gorgeous art
For fans of: Supernatural (or, more appropriately, the darker reaches of Supernatural fanfic); demons, angels and religious themes; gorgeous artwork; LGBTIQA characters; dark!fic