Rather than heavily featuring the returning cast from the previous seasons, Alice in Borderland season 3 has decided to focus on the new main characters that form a new cast and share the storyline with Arisu and Usagi, who continue to be the leads. Most prominent characters of the first and second seasons, e.g., Chishiya, are hardly there or only as cameos in the last part of the new season.
The third season is allotted six episodes, and the new characters are slowly introduced. Some are characterized by aggressive or manipulative tactics in the games, while others, through loyalty and teamwork, become friends. The new characters add a fresh dynamic to the season and highlight how the returning characters have evolved since the previous stories.
Disclaimer: The following article contains major SPOILERS for the show!
All the new characters in Alice in Borderland season 3
1) Yuna

In season 3, Yuna was initially presented as a member who cooperated with Usagi's team, frequently being their assistant and support during group game strategy. While playing the Possible Futures game, Yuna and her brother, Itsuki, got so engrossed in thinking about the future that they lost sight of the present.
The result of this concentration on the future was that they gave less attention to the present necessities of survival, which was the direct cause of Itsuki’s death. Yuna’s character journey revolves around her relationship with her brother and her part in the team, with the story emphasizing how choosing under pressure can change the situation for her and the people she loves.
2) Ryuji

Ryuji was first presented as one of the primary characters in Alice in Borderland season 3. He has been shown as a university lecturer who is very fascinated with the concept of near-death experiences and has a history of participating in the Borderlands games. Throughout the season, Ryuji cajoles Usagi to come with him to the games by calling on her sorrow for her father.
As a result, both of them are back in the Borderlands, where Ryuji is blessed with the opportunity to delve deeper into the afterlife and meet with his past collaborators. At the season's conclusion, Ryuji supports Usagi in escaping death, an important moment in his character arc and final destiny.
3) Tetsu

Tetsu, portrayed by Koji Ohkura, Tetsu in Alice in Borderland season 3 is first seen as a member of Arisu's team who is dealing with drug addiction during the games. Notwithstanding his struggle, Tetsu shows loyalty and a wish to help the team by always trying to find ways to participate in their saving. While playing Possible Futures, he is haunted by memories of his past and realizes that his decisions imply that he is going to a pre-set ending.
At the end of the day, Tetsu is resigned to his destiny and is removed from the game when he enters a chamber with inadequate points to proceed, thus dying. His journey is mainly characterized by the struggle between his addiction and his desire to stay with the team.
4) Itsuki

Itsuki is initially seen along with his sister Yuna during the Runaway Train game in Alice in Borderland season 3. He showcases strength and toughness to the last, which could be traced back to his firefighting experience in the real world.
During the Possible Futures game, Itsuki and Yuna become engrossed with the announced results of their choices. Such concentration causes them to select the future possibilities over their current survival.
Therefore, Itsuki's decisions in the game eventually bring about his demise in the last round. His plot is mostly left unstated during the season, and his death is offstage without much narrative expansion.
5) Sachiko

Sachiko Makino is brought in season 3 as a member of Arisu's team. She first outlines herself as a person who is not confrontational and quite friendly. The show propagates her troubled life outside the Borderland, thus giving the audience an understanding of her character. Sachiko is usually a bystander during the games, yet she is always supportive.
She quietly but not unfrequently contributes to the team's survival efforts. Her personality not only provides the team with another layer of emotional depths and their interplay of moods, but also the plot, especially when it comes to the theme of overcoming and persisting through hardships in the Borderland.
6) Nobu

At the beginning of the first arc in Alice in Borderland season 3, Nobu initially starts as a spectator who merely watches things unfold without interference. In the second game, Zombie Hunt, Nobu performs the tasks given to him by other players without question and even shoots a participant after being instructed to.
His relationship with Arisu, in the same way, helps him gain more confidence and be more assertive before the end of Zombie Hunt. Before the Zombie Hunt incident, Nobu confronts Kazuya, a disgraced Yakuza member, and convinces him to join their gang. Finally, Nobu manages to escape the game, thus earning himself a spot among the key players.
7) Rei

Rei Morikage is introduced in Alice in Borderland season 3 as a member of Arisu's team. She is described as a neurotic and thoughtful person who, through her careful and rational approach, can overcome the difficulties presented by the games.
During the Possible Futures game, Rei used the future projections solely to make group-beneficial moves and intentionally stayed out of their influence. She is portrayed as a tactful player who assumes a role similar to Chishiya from earlier seasons, bringing a calm and considerate presence to the team's dynamics.
8) Kazuya

In season 3 of Alice in Borderland, Kazuya is depicted as an ex-Yakuza individual whose first actions are those of an antagonist during the Zombie Hunt game. Without any sign of hesitation, he employed violence and showed a typical Yakuza mindset of doing anything to stay alive. After Nobu rescues him in the game, Kazuya shows his appreciation, and later, he actively supports Arisu and his team during the Kick the Can game when Arisu gets injured.
Through all the following games, Kazuya continues to be loyal to the group and bravely fights to the end. His plot ends with him giving up his life in the last moments of the Kick the Can game to help his teammates survive.
All episodes of Alice in Borderland are available to stream on Netflix.