Ja Wangnan seems to get along fairly well with the Regulars he met in the first part of the 20th Floor test and teams up with them for the Trustworthy Room Test. He eventually joins in a team with them. He likes to poke fun at people and teases them.
Nya Nia: At first it looked like Wangnan inspired Nia to retake the 20th Floor test with his determination. The two of them struck a friendship when they became roommates. When Wangnan found out the truth, he sympathized with Nia and forgave him, lying about being able to retake the test in order to make Nia feel better about his actions. Wangnan felt anger over Nia's death and swore to avenge him.
Jyu Viole Grace: From their first meeting Wangnan was intimidated by Viole and tried to avoid fighting him. Wangnan is mostly afraid of Viole, especially after Viole declared that he wished to see all of Zahard dead and Viole found his ring. Wangnan seemed to overcome his fear because of his desire to avenge Nia and his goal of creating a better place for people to live. Later on he appears to think well of Viole because of his personality and contributions to their team (mentioning how the team was 'mooching' off him). Currently Wangnan thinks highly of Viole because of his reasons for fighting, going as far as to reassure him that if he were to die, he would not regard him with malice. He also considers Viole a friend and wants to help Viole in passing the test as it is said by Akraptor before how was slacking in training but after meeting FUG he has been training hard. Near the end of the Workshop Battle arc, they both had a brief but gleeful reunion on screens. Even when captured by Karaka, Wangnan refuses to give up information on Viole.
Kim Lurker: From the beginning their relationship was antagonistic: Wangnan owed money and Lurker was a debt collector. Lurker bears a deep hatred for Wangnan and Nia for their hypocrisy and supposed pacifism, and tortures Wangnan mentally by having him listen to Nia's death via pocket. Later on, Wangnan wanted to kill Lurker as revenge for killing Nia, but decides that he didn't have a right to judge Lurker because he was the same type of person.
Yeon Yihwa: They were former teammates in a previous test in which they both failed after Yihwa set the whole team on fire, with only Wangnan surviving. He despised her since then, labeling her a 'team killer.' After joining Team Tangsooyook, their relationship improved greatly. They displayed efficient teamwork, as shown when they fought Cassano, and when they survived for a whole month alone together on the Hell Train while following Daniel's group. They still get into fights easily since Wangnan likes to tease people and Yihwa is easily annoyed by his antics. Wangnan especially likes to make fun of her because of Viole and her cooking. Their arguments are mostly petty and don't appear to cause any real harm or resentment. At the end of the Workshop Battle, she was seen caring for him while he was recovering from his injuries but she noticed his Zahard ring and his unusual recovery, wondering if there might be a bit more to him than it seems. Upon arriving at the Name Hunt Station, Yeon begrudgingly parted ways with Wangnan, agreeing with him that she would be more useful to Viole.
Hon Akraptor: Initially they were antagonistic to each other, but they are now on good terms (with some light teasing). Akraptor has helped Wangnan sort out his feelings on helping Viole. They have been seen teaming up in fights. He deeply cares for Wangnan, believing him to be a remarkable person and sacrificing his life for him, and remarking in a flashback that he views him as the heart of their team. After witnessing his murder by Rachel, Wangnan swore to get revenge for his friend, and later had nightmares about his death.
Prince: Prince initially saw Wangnan as inferior, often looking down on him and his attempts to pass the test. After they became a team, they still fought each other but it was less malicious and more petty. Even while they agree on a goal they argue about who wants it more. Wangnan was deeply affected by his death, having nightmares about both him and Akraptor on the way to the Floor of Death.
Yeo Miseng: Wangnan and Miseng were initially slightly antagonistic towards each other, as Miseng did not trust him and thought of him as incompetent and hostile along with Goseng. After passing the 20th floor test, Miseng and Wangnan trust each other more deeply, and Wangnan attempts to rescue her during the Workshop Battle from Verdi. After she and Wangnan become the only survivors after a failed attempt to capture Cassano, Wangnan wants her to return to Goseng and Horyang and forget about him, feeling like he failed to take care of her. Miseng, however, is loyal to Wangnan, and decides to stay with him and continue climbing. Miseng is still eager to prove to Wangnan and the team that she can take care of herself.
Khun Aguero Agnis: These two teamed up in order to get Viole back. Wangnan often makes remarks about how he regrets this since Khun rules their team like a tyrant. Khun often despairs over how idiotic Wangnan and his new team are. Despite this, Wangnan trusts Khun enough to follow his lead. Khun also acknowledges Wangnan's underlying leadership qualities and determination and was confident in his choice to spend points to put Wangnan in the workshop battle. Khun trusted him and Yihwa enough to throw them into the Train by themselves in order to disrupt Rachel's group.
Kang Horyang: Though not initially close on the 20th floor, Wangnan came to see him as family like the rest of his team. He was hurt by Horyang leaving for the Hand of Arlene alone, and tried to convince him during the Workshop Battle to come back to the team. After Horyang is left in a comatose state, Wangnan vows to bring Cassano back and rescue him, making it his primary goal until succeeding in sending Cassano back to him. Wangnan is willing to risk his own life and fight superior foes for the sake of saving him.
Rachel: Wangnan bears a deep hatred for Rachel for killing Akraptor and, through her counterplan, Prince. Despite that hatred, he is willing to work with her to get to the Floor of Death, both to keep Miseng safe and betray and kill Rachel later to make her pay. Rachel knows about Wangnan's ring and therefore the special status he has, and her hostility towards him is not personal. She is willing to grant concessions such as Cassano to Wangnan in exchange for cooperation, and shows remorse towards him for killing Akraptor.
Karaka: Wangnan is initially very distrustful and afraid of Karaka, but the two are forced to work together by circumstance on the floor of death. Karaka initially sees Wangnan as expendible and holds him hostage without remorse, but when Wangnan points out that they have matching rings, Karaka becomes immediately interested in him. Though he distrusts Wangnan, he seems to know about his past. An exchange with Viole on the Name Hunt Station implies that if Wangnan indeed has the ring, he may be Karaka's brother, though only Karaka knows it.