The year is 2030, society hasn't really changed or advanced any further than how you would expect. However that all changes on new years January something strange started happening to people around the world certain individuals now labeled Cyros began to mutate.

They changed warped into inhuman human looking things no longer themselves, Their mouths would split revealing sharp bug like mandibles, or an elongated tongue with chittering fangs.

Most individuals would have about a 90-80% human look the remaining 10-20% being their head or either their arms legs or back, sometimes growing one of either option between having alien like wings, claws, legs, arms, appendages, and tails.

Luckily at the beginning they weren't that smart and easy to deal with allowing humans to easily cull them revealing the population of those remaining. In the Initial stages the first wave struct the earths population at a insane 5.9 billion lives that's 70% of the population changed and culled. Over time every year from then on more individuals would become randomly infected.

Over time the only habitable place to live was Japan, during this time humans weren't the only ones getting used to this new world law. Cyros now introduced into the world began to grow more intelligent maybe a rare splice or mutation in their dna.

Soon they became split into two categories type A B and C. A type C Cyro had a more monstrous appearance losing their human appearance taking on a 80-100% monster look in appearance as well as having a completely feral mind akin to a wild animal. A type B variant has a 90% Human appearance capable of disguising itself amongst humans with a low intelligence barely capable of speak and merely mimicking seen behaviors to blend in it is suspected they live based on muscle memory from their host original memories allowing them with their low intelligence to remain undetected. They have a generally feral and low IQ mindset solely focused on survival and animalistic needs. Lastly is the A variant, these variant have Human level intelligence, allowing themselves to blend in amongst humans perfectly with a human physical appearance of 90-100% they generally hide their appendages and are almost impossible to distinguish aside from their eyes and tongues being the only things they cannot hide very well while they can hide their real eye with a thin membrane like sheath that hides it with a fake looking pupil if flashed with a bright light the sheath will retract revealing the real eyes. Their tongues while capable of morphing into looking like a humans if pulled can be extended at a minimum of 5 bypassing the human physical limit.

About 5 years after all of this scientist Discovered the cause for the Cyro a parasitic alien like virus entering body.This foreign organism digs it's way into the body and depending on where it gestates causes the host to become either of the A-C Cyro variants. Type A being that it managed to enter and assimilate with the brain. B being it managed to merge with the spine. C Bing anywhere else In the body causing it to allow its change in appearance completely. Albeit because the data from the brain nor spine was taken it remained feral in nature leaving no traces of intelligence nor humanly appearance.