Aiyoku no Eustia (穢翼のユースティア, literally "Eustia of the Tarnished Wings") is a Visual Novel distributed and developed by August, released in 2011 on PC, with a later port on Play Station Vita in 2014. There exists no official English translation of the game, but a Fan Translation is in the works.
Long ago, Angels were sent to the surface to guide humanity with God's wisdom and powers, leading it to everlasting prosperity and a golden age. However as time went on, mankind eventually stopped relying on Him, causing Angels to disappear and flooding the earth. As many humans died during the process, a priest by the name of Irene and her disciples prayed to God and asked for forgiveness. Her wish was granted, saving mankind from disaster, which now lives in the floating city of Novus Aether, created from the wishes of Irene, now revered as a saint.
Hundred of years later, Irene's power was cultivated through generations of priests to keep the city afloat, still considered to be the last bastion of humanity, with the current one known as Saint Irene the 29th. However, a tragic incident caused a portion of the Lower City to collapse 10 years ago, and is now remembered as the "Gran Forte".
In time, the lowest layer of Novus Aether became the dwelling of all kinds of low-lives, people who lost much of their former lives during the "Gran Forte", becoming known as the "Prison". However, a contagious disease which causes people to grow wings has spread throughout the city, and a unit has been formed to deal with these people swiftly.
In this "Prison" resides Caim Astraea, a freelance ex-assassin who does odd jobs for his friends for money, refusing ones that require him to kill people. During one request, Caim finds a girl who contracts the wing-disease, enveloped in a light that reminds Caim of the “Gran Forte” years ago...
Aiyoku no Eustia features the following tropes:
- After the End: The story is set in a post-apocalyptic world, where the living remnants of humanity gathered in a single floating city.
- Crapsack World: Through the eyes of Caim and the others, it's made clear that life in the Prison is the worst thing that could ever happen to anyone, especially with most women who are forced to work as prostitute to make a living. The Lower City is no better, albeit it doesn't have widespread poverty.
- Layered Metropolis: Novus Aether was at first separated between the luxurious clean Upper City and the average Lower City. Then the Gran Forte happened, created an even Lower City known as the "Prison" and with extremely poor living conditions and almost no contact with the outside.
- Neighbourhood-Friendly Gangsters: The "Uncorroding Golden Chains", the group whom Caim works for, is a quasi-governmental entity with enough influence and power to keep a semblance of order in the "Prison", protecting numerous shops and whorehouses in the district.
- The Plague: The "Wing-Growing Disease" is one of the main problems of the story, as a seemingly incurable disease which kills without fail. Its means of transmission are unknown, but presumably airborne.
- Quarantine with Extreme Prejudice: Downplayed. People infected with the Wing-Growing Disease are actively searched by the Quarantine Department and put them in lockdown to contain the plague and treating the winged humans. However, they can resort to force if necessary, and their lapses into violence caused them to be derisively nicknamed as the "Wing Hunters" by the inhabitants of the Prison, in which they regularly intervene.
- Streetwalker: Many prostitutes of the Prison often do this, mostly out of necessity.
