Gotou is a unique and exceptionally powerful creature who serves as a primary antagonist. His background is distinct from ordinary members of his species, as he was not a naturally occurring being but rather an experimental creation, brought into existence by another parasite named Reiko Tamura. What makes Gotou fundamentally different is his physical composition; his body is not a single parasite controlling a human host, but a fusion of five individual parasites that have unified into a single entity. These five beings occupy the head and all four limbs, functioning together as one cohesive and terrifyingly efficient organism. The name Gotou itself is a play on words, as the character for "go" can mean five, referencing this unique aspect of his nature.

In terms of personality, Gotou is portrayed as highly intelligent, cold, and calculating, even among his own kind which is often characterized by a lack of emotion. He carries a profound superiority complex and views human beings as little more than trash, showing no remorse or hesitation when dismembering opponents or taking lives. Despite this arrogance, he is not purely a mindless killer. Gotou is known for his patience, often observing his enemies and waiting for the opportune moment to strike. He has also displayed a degree of honor or respect, occasionally complimenting worthy opponents like Shinichi Izumi and his parasite partner Migi on their strategies, and acknowledging the noble attempt of a soldier who tried to shoot him. While he holds humans in contempt, he remains cooperative within the group led by the human politician Takeshi Hirokawa and respects Reiko Tamura, the being who created him, showing a capacity for loyalty and cordiality.

Gotou's primary motivation is a simplistic and primal one, especially when compared to other parasites who might question their existence. He has explicitly stated that he lives only to fight. Combat is the entire purpose of his existence, and in battle, he is most complete. He has little to no interest in the more complex plans or philosophical questions that occupy others of his species, embodying the pure, distilled fighting instinct of a parasite.

Within the story, Gotou serves as the most powerful and persistent threat that Shinichi Izumi ever faces, effectively becoming his archenemy. For much of the narrative, he operates as the enforcer and a key member of Takeshi Hirokawa's organization of parasites, which has infiltrated human political structures. His role is to eliminate threats, and he is eventually tasked with killing Shinichi, who has become a significant problem for the group. The confrontations with Gotou represent the peak of physical danger in the series, forcing Shinichi and Migi to push themselves to their absolute limits in a fight that seems nearly unwinnable.

One of Gotou's most significant relationships is with his creator, Reiko Tamura. While she views him as a successful but fragile experiment, he shows her a degree of respect and is shown to contemplate her ideas. He also shares his body with other consciousnesses, the most notable being a parasite named Miki. Gotou is willing to allow Miki to take control of the body on occasion, stating that the other needs more experience. His relationship with Shinichi is purely antagonistic, defined by their deadly encounters. However, their final confrontation takes on a more complex tone, as Shinichi hesitates and weeps for Gotou's struggle to survive, recognizing a right to exist even in his enemy.

Gotou undergoes a notable transformation and a form of development, both in power and in mindset. Early on, he had not fully mastered his complex body, using his violent attacks on a yakuza office and even practicing the piano as methods to practice coordinating and unifying the five separate parasites within him. Over time, he achieves perfect "command" of his composite form, becoming an even more terrifying and efficient predator whose brainwaves blend into one. When pushed to his limits, he evolves into a monstrous, more primitive state, growing to three meters tall, gaining a gray, muscle-like exterior, multiple arms, and a tail. In this form, his thoughts become more aggressive and animalistic, focused purely on survival and extermination, a shift that ultimately contributes to his downfall.

The notable abilities of Gotou are what make him virtually unstoppable. Because he is composed of five parasites, he can weaponize his entire body. Every limb can transform into a blade or a shield, allowing for multi-directional attacks and unparalleled defense. His physical capabilities are far beyond any standard parasite. He can run alongside a truck traveling at sixty kilometers per hour, morph his legs to leap through trees with agility surpassing a monkey, and harden his skin to withstand close-range shotgun blasts and even a direct hit from a grenade launcher with only minor damage. His combat speed is high enough to dodge bullets by reading the aim of his opponents, and he has effortlessly slaughtered entire squads of heavily armed soldiers in seconds. Despite this overwhelming power, Gotou does possess critical weaknesses. He has small chinks in his armor, one on his lower left side. More significantly, the parasites within him are highly susceptible to toxins. It is a poison, introduced into his body via a rusty metal rod, that finally destabilizes his control over the other beings, causing them to rebel and leading to his ultimate defeat.