Arisu is the main protagonist in the show. Before the borderlands, Arisu was a unemployed young adult living in his parent's house and he hung out with his two friends Karube and Chota a lot. But in the borderlands, Arisu lost both of his friends which impacted him greatly, but he was very intelligent and with the help of Usagi he completed most of the games. Which also caused him to be a diamond game specialist  (Diamond games involve lots of critical thinking)

Usagi is the second main protagonist in the show. Before the borderlands, she would climb mountains with her father and would spend a lot of time with him. Until one day her father left for the mountains and was never found again. Usagi is a very brave person and is very empthatic. And due to Usagi being very athletic, she is a spade games specialist. (Spade games requires lots of physhical strength)

Mira is the main antagonist and has been in the borderlands longer than Arisu and Usagi. She has completed all of the past games and chose to become the Queen of Hearts. She had created most of the hearts games and tried to trick Arisu in her own game. Mira lacks empathy for others, and she is very manipulative and loves to lie. 

Kuina is one of the people Arisu and Usagi met inside of the games. Before the borderlands, Kuina did martial arts with her father as her teacher. Kuina's father was not happy about Kuina wanting to become a girl and even destroyed all of her belongings in a fit of rage. Kuina was called weak, and was kicked out of her father's martial arts dojo. Kuina then moved in with her mother and eventually got her surgery. Kuina is a sweet,playful character in the show and is a club games specialist. (Club games involve teamwork, and working with other people in order to complete the game.)

Ann is one of the people Arisu and Usagi met inside of the games. She was a beach executive and worked for the police. She is very adventurous and wants to find more about the borderlands and the limits. Ann is also very smart and uses her own unique ways to complete games. She was the first person to test Arisu's intelligance and was interested in how he would complete the games. Ann is a diamond game specialist.

Chishiya is also one of the people Arisu and Usagi had met inside of the games. In the show, Chishiya mostly keeps to himself and prefers toparticipate in games by himself. He doesn't really involve himself with the other people in the games. Chishiya is very smart and obersant and doesn't trust people easily. Before the borderlands, Chishiya was a doctor in training. Chishiya is a diamond game specialist.