Tiny creatures called "Parasytes" have arrived on Earth with the sole purpose of taking over human brains and preying on mankind. One latches on to ordinary high school student, Shinichi Izumi. Whilst he is able to fight it off before it reaches his brain, it is now stuck within his right hand. But a strange relationship develops between himself and the creature he calls "Migi," and before long they begin to encounter other Parasytes which launch savage attacks against them and endanger the lives of his friends and family. Shinichi and Migi have no choice but to work together and hurl themselves into the fight against an ever more complex and aggressive enemy.