Absurd but creative and well executed action story. Mysterious intelligent shape-shifting parasites target humans and try to replace the head of the host to gain full control of the body, imitating host behaviour. Teenager managed to avoid death by applying tourniquet on his arm where parasite burrowed, so parasite replaced his arm. Now, two intelligent creatures have to agree on symbiotic behaviour to survive, being at odds with humans and parasites. They have to learn to compliment each other's abilities, coordinate and understand each other through verbal communication (protagonist actually talks with his "hand").
The show is not afraid to touch philosophical questions. In one episode, an intelligent life form struggles to understand humans, noticing that every creature is born with a command (e.g. spider is born with command to build webs) but humans are born as blank pages... What might be their purpose?
Some moral dilemmas are presented and well entertained.
There is a lot of action, drama and horror.
https://myanimelist.net/anime/22535/Kiseijuu__Sei_no_Kakuritsu
