This papercraft is Migi, the name given to the parasite that infested Shinichi Izumi's right hand, based on the sci-fi horror manga series Parasyte (Japanese: 寄生獣 Hepburn: Kiseiju), the paper model is created by youlingke.
Migi is unlike most other parasites in the series. He didn't develop an urge to eat other humans due to not consuming the brain of the host, and this also allowed Shinichi to also retain his individuality. Being two separate entities give Migi and Shinichi a two on one advantage in most fights and can allow them to both learn from each other to become better. Migi is shown to be tactical in battle, a characteristic even Shinichi acknowledges. In battle, he tends to measure the strength of the opponent and is shown to be merciless. Migi, like most parasites, is fully capable of transforming into a weapon to fight off other parasites and feels no emotions or remorse in killing his own kind to survive.
Migi is a parasite and as such lacks the emotions of a human being. His main goal is to keep him and his host alive, even if that means killing his own kind. Migi often thinks of Shinichi as a threat because he is always getting into fights to save others, and he once threatened to cut off Shinichi's arms and legs to stop him from getting them in any danger and will attempt to kill his friends if they find out about him.
Throughout the series it is seen that Migi becomes more human, sometimes even showing respect towards others and curiosity towards things, While Shinichi becomes more like him.
Migi can change his forms depending on the situation, and as such he doesn't have a definite appearance. He can turn the arm into a blade or create human like eyes and a mouth to communicate. Most parasites are limited to only being able to mutate the area in the body they merged with making them look similar, but Migi is an exception because he did not make it to the brain of his host and is only able to change the shape or the arm instead. [Source: wikia]
You can download this papercraft template here: