The story centers on Kuon Kanae, a junior high school student who was in Tokyo on the day white feathers fell. Kuon sometimes sees feathers on people's back, and sometimes sees the sky filled with black letters…
 
(Source: Anime News Network)
 
Note: The manga takes place after the story of Tenshi Kinryouku (Angel Sanctuary), but it is an independent work.

Why is Setsuna so mixed up? Despite his attempts to be noble, he'll fight anyone anytime; he ignores all authority; and he harbors feelings for his sister that can only be described as "incestuous." Why is he such a mess? The reason may be found with two demons from the underworld and their enemy, an insane angel who is distributing an insidious computer game called Angel Santuary.
 
(Source: Viz Media)

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