Kusano

Kusano is aggressive, distrustful and highly concerned with threats to his species. He advocates eliminating Shinichi rather than tolerating the risk posed by a human who understands Parasite biology.

He becomes particularly suspicious of Reiko because she repeatedly refuses to behave according to the straightforward survival logic he expects from another Parasite.

Kusano is capable of cooperating with others but has little loyalty when an ally becomes inconvenient. His behavior also demonstrates increasingly recognizable anger, one of several indications that individual Parasites can develop more complex emotional responses.

Kusano possesses the standard abilities of a mature head-infecting Parasite. He can reshape his head and neck into hardened blades and other weapons, maximize the physical output of his host body and sense nearby Parasites.

His Parasite tissue can remain active after separation from the host for a limited period, although he still depends on a functioning human body for long-term survival.

Kusano is an experienced combatant but lacks the extraordinary cellular control demonstrated by Ryouko Tamiya.

Kusano operates within Takeshi Hirokawa's organized Parasite community and becomes concerned about Ryouko's increasingly independent behavior.

He argues that Shinichi Izumi represents a threat that should be eliminated and interprets Ryouko's refusal to support that decision as evidence that she can no longer be trusted.

Kusano eventually conspires with Hikawa and Maesawa to assassinate Ryouko. She anticipates their numerical advantage and divides her own Parasite tissue to fight them simultaneously, defeating all three conspirators.

Ryouko Tamiya begins as Kusano's associate, but his distrust of her grows as her interest in humanity deepens. He eventually attempts to kill her and is defeated.

Takeshi Hirokawa leads the political organization with which Kusano is affiliated.

Shinichi Izumi is considered dangerous by Kusano because he understands Parasites while retaining a human mind.

Hikawa and Maesawa join Kusano in his attempt to assassinate Ryouko.