An action anime that feels like a superhero tale, but the hero shares his body with a parasite species that gives him the power.

The plot is interesting enough, what you would expect from an action anime - the protagonist must save others from his city from the parasytes, creatures with the power to take control of the host's body by eating and merging with their brain. It has a commentary on human nature and its destruction of the planet, and how the parasites hold a symbiotic relationship with humanity, as they are nothing more than living beings driven by the instinct of survival.

Such commentary falls a little short and can get overly expositionary at times. Much more interesting is simply to see how the individual characters evolve and how they contrast with their other counterparts. The protagonist struggles to keep his own humanity, while another man sharing his body with a parasyte seems to do so effortlessly. The parasytes themselves, some just being driven by instincts, while others feel 'tainted' by the humanity they are being exposed to.

While the plot isn't overly unique and original, it's still interesting to watch as the characters develop, struggling with their original nature vs the experiences they have along their way.