Digital monsters, most commonly referred to as digimon. There was once a time when only a rare few knew about these creatures, and the digital world, the alternate world which they came from. But things are different now. Everybody knows about digimon, they now appear in our world frequently, with varying motives.
Also most humans have one as a partner, one that hatched from an egg that materialized in front of them on their tenth birthday, along with a digivice. These digimon help us with our everyday lives. It is possible through a strong bond and the use of a digivice for a digimon to digivolve; however doing so past champion is rare, and only tends to happen in crime fighting agencies
Digimon have always been one of three attributes. Data, the most common, these digimon are known for being either good or evil, depending on the digimon itself. The Vaccine attribute, these digimon are known for being pure and good, and no righteous person would lift a finger against one, or their partner, if they have one.
And then there is the Virus attribute. Believed to be purest evil, the most notorious digital villains have been of the virus attribute. A long time ago a law was passed. All virus digimon were to be captured or deleted on sight. A special group was set up, the Virus Containment Agency, or VCA, that dealt solely in dealing with virus digimon.
Most people were happy with the new rule and the VCA, it made them feel more safe. However there were a few who weren't. Those who had viruses as partners, because they were not spared from the rules. All viruses were evil, and had to be deleted before they could cause trouble. Anyone who had a virus digimon was expected to give them up for deletion. Most did, but some, those loyal to their digimon partners, did not. They fought against those trying to take their partners away, and ran off into deserted areas, hiding from the VCA, knowing if they were caught their partner would not only be deleted, but they themselves would be arrested, having now become criminals for resisting, and aiding viruses.
They always say there is safety in numbers; small groups now dot the world, consisting of resisting viruses, who banded together for better survival. Most are just trying to hide and survive. Some fight against the VCA. However other groups were formed for an entirely different reason. To fight ,but not the VCA or the law, but something else. Something that endangers the human world, something the VCA, with their prejudice, are too blind to realise.
Because you see, not all viruses are evil. And not all vaccines are good.