Kusano

Kusano (草野, lit. Kusano) was one of the parasites responsible for the deaths of Kuramori's wife and their daughter. He suspected that Reiko Tamura was a traitor and, along with Maesawa and Hikawa, tried to kill her.

Appearance
He had short black hair, with an average height and build. He was seen wearing gray dress pants along with a black pinstriped vest and a gray long-sleeved shirt.

In the manga, he appears to have a small scar above his left eye.

Personality
He is reactionary and aggressive against perceived threats, advocating for Shinichi Izumi to be killed and trusting his instinct that Reiko was no longer an ally due to her decisions. He is disloyal even for a parasite, willing to kill parasite allies if it meant getting rid of Reiko and keeping his plans secret from the higher-up members of their group. It's noted that he later begins showing impressive signs of expressing anger.

He appears to help lead the parasite group, managing a laptop in a meeting in the anime and holding onto files involving Shinichi in the manga. He also persuaded two other parasites to assist him in destroying Reiko.

Reiko later comments that he is similar to A, and that his plans had little creativity.

Plot
Kusano is first seen driving Gotou around the corner from a building where the Yakuza were holding a meeting. He comments on Gotou's appearance when he returns and drives off. They return to their headquarters and inform Hirokawa of their success. As they leave, he reminds Gotou of Reiko's maternity leave.

He is later seen during Hirokawa's campaign speech, standing on top of the stage with Hirokawa, Gotou and three other people.

He partakes in several meetings between the other parasites and Hirokawa, often advocating to eliminate Shinichi and expressing distrust for Reiko's plans when they could potentially expose the parasites.

Following the death of a parasite that's killed by Shinichi in a restaurant, the parasites hold a meeting to decide how to handle the situation. Kusano questions Reiko's continued defense of Shinichi, asking if having a child changed her and suggesting she get rid of it. Eventually, the group comes to the conclusion that Shinichi has to be killed. Miki volunteers to deal with him, though both Kusano and Reiko are skeptical of his chance of success. The evening before Miki goes to hunt down Shinichi, she and Kusano burn down Kuramori's office. Kusano then sends her alone to take care of Kuramori himself, and she kills his wife and daughter in an attempt to wipe him out.

Upon realizing that they failed to actually take out the detective, Kusano and Hikawa hold a meeting with Reiko, with Kusano blaming her for everything that's happened after she praises his capacity for anger. In return, Reiko tells them she never expected them to fail so miserably at killing Kuramori. She then states that in killing his family but leaving him alive they have made a worse enemy, warns them not to underestimate the human race, and explains that the true power of the human species is their sheer number. However, because her way of thinking is so unusual, Kusano later decides she is a threat and must be killed.

Kusano, Maesawa and Hikawa confront Reiko later one night, emitting strong signals of animosity that lures Reiko to their position. After trading words, with Reiko comparing Kusano to A and commending their individuality in deciding to kill her, and Kusano informing her that Gotou and Hirokawa know nothing of their plans, Reiko makes her escape. While chasing her down, he initially decides that it doesn't matter who sees them as long as she's killed. Sensing that Reiko split herself in two, Kusano follows the section containing her human portion into the city. However, she runs into a large crowd, laughing madly and making a spectacle of herself. Believing that she had lost her capacity to think, Kusano hesitates to follow her in front of so many witnesses. He soon senses a parasite's death and hurries back to the battle between his allies and the other fragment of Reiko.

At the construction site, he begins attacking Hikawa, who is having her body destroyed from the inside. He claims that he can't be sure who's in control, due to her trying to get close to him. As Hikawa begs for her life, he mocks her while dismembering her body and drawing her animosity. After killing her, his body is slashed into three pieces by the body attached portion of Reiko, who had snuck up while he was focused on her detached portion. Trying one last time to kill her, he is easily knocked away and begins to die. Reiko leaves him with a quick explanation of her deceptive strategy and he shrivels up and dies.

Abilities & Powers
Being a parasite, Kusano can shapeshift from the head up and and harden his cells for offensive or defensive purposes, as well as detect other parasite signals and automatically emit his own. He can also maximize the host body's physical potential and disregard pain.

Kusano is one of the few parasites shown to transform his parasite body into a mobile form after he was detached from his host.

Weaknesses
Like all parasites, Kusano requires a host body with functioning organs to survive, and would die if he were separated from the body or it was destroyed. Fire can cause his parasite cells to "freak out", making him lose control. He is also susceptible to poisons or caustic chemicals, which would either kill parasite cells on contact or make his host body fail.

Although he attempted to overpower Reiko with greater numbers, his ruthlessness caused his death as he left his teammates to fight half of Reiko on their own and eventually killed Hikawa himself when she was forced to threaten him.

Trivia

 * The name Kusano means "grass, weeds" (草) (kusa) and "plains, field" (野) (no).
 * Kusano appears in the Parasyte Reversi spinoff.