Project ARMS

Angry People with overpowered arms! 

In both series the characters have supernatural abilities that transform their limbs. 

Both cyber body horror stories. Main character is given nanite virus that threatens to destroy the world. There are secret societies and fast paced fights in both.  

They are flawed animes from the early 2000's that are still remembered to this day for their funny English Dubs. 

both contain humanoid mutants as well as loaded with innate conspiracies 

Both titles feature the main character (Shinichi in Parasyte and Ryo in Project ARMS) that has a mutated right arm that gives them superpowers. In both series, the main hero has another life form that lives inside their right arm (Migi in Parasyte and The Jabberwock in Project ARMS) that can change forms depending on the situation. The main character in both shows dislikes killing, but will do so if necessary. Both shows also have a good mix of action and drama. If you enjoyed one, you will enjoy the other.  

Both share a similar story, The main characters of both are young men who gain alien power which they dont fully understand, but use in defence of them selves and their friends against an enemy who could be anyone. Both are full on action, strong story, great pace. All around fun anime aimed at a maturer audience 

While the plot isn't the same, the ARMS are similar to the Generators (Enhanced Humans). 

Like in witchblade plays this anime around an intrigue of two big companys who rule the world. 

People can transform into battle ready forms, Government conspiricy. Can't trust no one, always in danger, And when shit hits the fan, the heroes kick ass