Premise and setting
What if a secret government project was using youth to handle weaponized demons? What if those demons were copies of one of their close friends?
Movie/novels: Solaris (for the concept of the demons and their needs)
Manga/Anime/Video-games: Ghost in the Shell, Neon Genesis Evangelion, Blame & Biomega (from Tsutomu Nihei), Parasite Eve and Parasyte.
In a Ghost of the Shell like future, after a expedition on Venus, a alien virus breakout on Earth. The virus transform people in bio-organic zombies who tries to eat each-other. The majority of the population is infected by the virus but don’t develop any symptom. No cure exist and no cheap and practical way of detecting the virus on a large scale exist.
Some city have fall down and turned to chaos but most big city prevail and shanty towns of refugee coagulate around the walls of the major mega-city.
A international operation have been formed by the UN to try to control the infectees and to develop a vaccine again the alien virus.
Unknown to the public, Operation Caduceus discovered that some of the infectee mutate into huge bio-mechanic entity who try to meet each other. Those entity have been identified as a major threat for humankind.
Everything changed for operation Caduceus after that the infected daughter of their lead researcher mutated into a titan entity and survived the process. Her identity have been assimilated by some kind of hivemind that exist within the bio-energetic field formed by the bio-mass of the alien virus.
Patient zero was quickly moved away to studied and cloned to try to weaponize her biogenetic material. Their result were code-named Erinyes or ERIN: human-like clones of patient zero who seem to manifest some of the titans super-human abilities. Those clones remained brain dead until it was discovered that some people who knew patient zero could active them and made them react to their presence.
Counter Bio-terrorism Unit Oreste:
CBTU Oreste was selected to field the first operational ERIN units. Their performance on the field remain to be seen and tested.
The player characters:
They are kids who knew patient zero and who have been recruited to activate and to handle her weaponized clones. Their link with patient zero attract the echo of her identity within the virus hivemind and through their memories of her they can manipulate and command emanation of this identity. Or at least this is what the researchers of project Persephone could theorize. Those echoes will menace their humanity by tempting them to believe that they are truly patient zero, to constantly revive the past and to slip and fall within their collective memories to be assimilated by them.