|Species|| Human (formerly)
|Position||Heavy Weapon Warrior|
|Hair||Blonde (later on with Black Streak)|
|Voice Actor||Lex Lang|
Kay Zanestin is another student of Class 4-A that disappears into teh Lost World Eden. Augmented as well, he awakens with Newt Sangster and Lex Hammond, although in the more hostile but not frozen forests near the mountains. He becomes the Heavy Muscle of the Sangster Group, and later on one of the Heavys of the Grant Group/Guardians.
- Name: Kay Zanestin
- Nickname: Zaji
- Age: 18-19
- Hair: Black (later on with Blonde Streak)
- Eyes: Dark brown
- Likes: Manga, girls, Onna, working on cars, his family, Maya (best friend), his friends, working out, combat fighting, being of help to others
- Dislikes: His father, anything not meat, bullies, traitors
- Family: Father, Mother (deceased), Stepmother, grandparents, older sister
Before he is taken to the Lost World, Kay appeared as a dark-skinned muscular man. He wore a long singlet that was rugged and torn at the bottom. The singlet was usually accompanied by text saying something like "Reflection". Kay also wore the usual blue jean slacks and also white sneakers. Kay had blonde hair that was not only long, but spiky. He usually was seen with a white bandana around his head. He was relatively tall and also has been seen swapping his shirt around as seen by the different text.
After taken to the Lost World, his figure is increased and augmented beyond anything known back to where he was from. Kay gained a teenage medium muscular look of an athlete, and gains a boosted height of 6’9”, taller than any of the boys. His hair also gains a black streak from sides to back.
He was both childhood friends with Masakazu and Maya. He once attended Miyauchi's dojo, but quitted pretty soon and was seemingly ditched by Masakazu when Kay's grades dropped. He didn't have a good reputation at school and people thought him as a delinquent. The first girlfriend he dated was also a friend of his sisters. In Maya's memories, it seemed he had no friends in school and his only friends were children.
In his childhood, he lived with a complicated family who mainly didn't care for him. In the outside, they did look like a loving and happy family, but however it was noticeable that none of his family paid any attention to Kay, which he knew. His real mother had actually ran off with another man and his father quickly remarried whilst his new mother didn't care a bit for Kay and only paid attention to his sister. His father was also someone who didn't care for children and acted as if Kay was invisible that made it seem that Kay was a person who actually lived alone even in his own house.
Kay originally appears as a carefree, perverted delinquent. At first, he was someone who complained about not wanting to die during the epidemic case and someone who was often messing around and enjoying himself. As he has a crush on Kanako, he is constantly seen trying to impress or partner up with her throughout the story (which pays off when after the Gigantopithecus arc and he’s recovering, she tells him she feels the same, and the two kiss, becoming a couple).
He also comes across as a tough and strong individual, despite his common perverted jokes and antics. During the story, he was commonly not recognized by the others which caused him to blush and show embarrassment. He has also shown to get angry or frustrated easily and also bring out his anger in violent means as seen by both his actions towards Masakazu and Shirou Mariya.
Despite this, he is also someone who is kind and determined to protect anyone he considers a friend. He isn't afraid to put himself in danger for other people and later is even ready to put his own life in danger despite anything to save Kanako during the kidnapping case. He was always like this too, when wanting to save Masakazu. He also regretted not being able to save him during his time on the Cursed Mountain, he was having illusions of Masakazu attacking him. To him, he considers all his friends apart of his own family because of his complicated family history. Despite his perverted nature, Kazuma would never force a girl into anything they were uncomfortable with, showing greater moral fiber than most males in the series.
- Male Augmented Human - Heavy Class
- Strength: It has been showed that he has good strength as he was able to hold an Andrewsarchuse's mouth down with his arm. Later on in the story, it is shown he’s not afraid to fight back and fight smart. He had knocked out a Cheetah Raptor with a clean blow to the head, as well as evade the other raptors until Riley and Anna arrived to help him escape.
- Fighting Skills: Kay, when he was younger, attended a dojo with Maya Miyauchi, hinting that he might have some basic martial arts skill.
- Steel Club: Made from the jaw of a GroundBreaker, the materials the club's made of is rather durable and strong, able to fissure the earth he strikes with enough force.
- Assault Mini-Gun