Sun is a student at Haven Academy.
Neptune is an old friend of Sun and a member of his team. The pair share a close bond of familiarity and tease each other in a good-natured fashion. Sun seems to dislike it when Neptune acts like a "nerd", as seen in the library when Neptune says that libraries are meant for reading. Sun seems to have a close relationship with Neptune as he was the main member of the team to coax Neptune to help Team SSSN win against Team NDGO.
Although interactions between the two have been few, Sun seems to get along well with Ruby. He seems willing to help Ruby and her team in their investigation with the White Fang, telling her that friends should always get involved with each other's plans.
In "Battle of Beacon", Sun is willing to let Ruby borrow his Scroll to summon her weapon after her Scroll was destroyed by Mercury Black. Later, in "End of the Beginning", Sun tells her that she had better come back after she and Weiss Schnee decide to return to Beacon Tower to save Pyrrha Nikos and Jaune Arc.
Although unaware of it, Sun Wukong is seen as "riff-raff" by Weiss, who has prejudices against Faunus due to her family's history with the White Fang.
Despite her lack of trust, Weiss appears somewhat grateful towards Sun for helping Blake when she runs away; although she says that she is "still not quite sure" how she feels about him.
In the Beacon Academy library, Sun refers to Weiss as "Ice Queen", implying he holds a negative view of her personality. Sun seems to be oblivious of Weiss' annoyance to him casually hanging in front of Team RWBY's dorm room window in "A Minor Hiccup" just after the girls were finished changing clothes; at Weiss' inquiry to what he means "he does that all the time", he clarifies that he climbs trees all the time, which only annoys her even more.
In "Battle of Beacon" Sun expresses concern for Weiss when she runs off with Ruby to save Pyrrha and Jaune, telling her that they better be back. This shows that he cares for her to some extent.
Sun Wukong developed an attraction to Blake when he first saw her. In addition, he suspected Blake was hiding something under her bow.
Sun was the one who comforted Blake after she fled from her teammates, and they quickly formed a friendship. Although his petty law-breaking annoys Blake, she had sprung to his defense when Weiss was speaking ill of Sun earlier.
At the same time, Blake's quiet and reserved demeanor causes Sun to tease her a little. Even right after they first meet, Sun seems to be somewhat protective of her, shown when he jumps in to help her during her fight with Roman Torchwick. Both seem to work together well during the following fight.
Sun continues to pair up with Blake during her investigation into the activities of the White Fang. Later, he nervously invites her to the dance only to be shut down by an unstable Blake. This clearly hits him hard, as he appears to be rather downcast afterwards.
After Blake is convinced by Yang to ease up on the investigation, she makes up with Sun, and they go to the dance together. The two are later seen dancing and smiling, indicating that Sun's attraction towards Blake may be mutual, further evidenced by how he talks about her with Neptune.
In "New Challengers...", Sun points and winks at Blake in the audience while he and Neptune are celebrating their team's victory in the match against Team NDGO, and Blake blushes in response.
Later, in "End of the Beginning", Sun saw Blake run away, offscreen, after they had reached Vale.
In "Of Runaways and Stowaways", it is revealed that Sun has been following Blake after the Fall of Beacon instead of returning with his team to Mistral. Sun reveals himself to help Blake and the ship's crew defeat a Sea Feilong, but Blake is irritated that Sun has been following her for months. Sun explains that he believed Blake was going to take an offensive against the White Fang and wanted to help her. When he discovers the truth that she instead wants to sort out her own personal issues, he is still willing to accompany her as she travels home to Menagerie, stating that Grimm are getting more dangerous and the White Fang may still pursue her even if she tries to stay out of its way.
In "A Much Needed Talk", Sun and Blake's relationship becomes strained after he tries to warn her about the White Fang. Despite it, Sun is still willing to go after her when she chases after a spy.
In "Taking Control", after waking up from being unconscious, he tells Blake that he would do it all over again to protect her and that shutting out the people who care about her enough to fight by her side only hurts them more.
In "Necessary Sacrifice", Sun helps Blake in signing people up for the defense of Haven, though their efforts prove to be useless. When they take a break, Sun is pleased when Blake associates him with the word "earnest". When he brings up that they will have to face Ilia again in the future, he is surprised that he has inspired Blake into trying to save Ilia from Adam Taurus' influence in the same way he has been there for her.
In "Alone Together", he rescues Blake from being captured and then helps her to go rescue her parents from being assassinated. In "True Colors", Sun is angered when he finds Blake on the ground and attacks Ilia as a result. But he ceases his attack when Blake tearfully pleads for him and Ilia to stop fighting. After Blake rallies the people of Menagerie, Sun tells her that they have work to do and earns her thanks.
After the Battle of Haven, in "Argus Limited", Sun promise Blake that she has not seen the last of him and they will meet again in the near future. After they go their separate ways in good terms, Neptune asked Sun if it was alright for him to letting her go, but Sun said that it was never about that, he just needed to go back to his team to be a better leader.
In The World of RWBY: The Official Companion, it is stated that Sun is one of Blake's former suitors.
Despite only being shown having a few interactions, Sun also seems to get along well with Yang as well.
During "End of the Beginning", Sun looks after an injured Yang and Blake at Ruby's request. Later in the episode, it is implied that Sun personally told Yang that Blake left.
At first, Sun tries to make a good first impression on Blake's parents. Although he manages to win over Blake's mother, he does not manage to impress her father, as Ghira bluntly tells Sun he really does not like him multiple times. Sun is thoroughly intimidated by the man. As of "Unforeseen Complications", the mutual respect between Sun and Ghira has been steadily growing. Prior to his speech to the people of Menagerie, Sun gave him a gentle reassurance, which Ghira is grateful for. In "A Perfect Storm", Sun saves Ghira from being gunned down by the White Fang. Teaming up with him against Corsac and Fennec Albain, Sun promises not to let Ghira down, though he is immediately told to shut up.
Kali on the other hand immediately takes a liking to Sun, appreciating his talkative and friendly nature. She enjoys hearing stories of her daughter and Team RWBY from the young Faunus and tends to make casual asides that embarrass her daughter in front of Sun.
Sun and his team remain on friendly terms with team CFVY. After the Battle of Beacon, the two teams reconnected in the settlement on Coquina, where Sun caught his peers up on what had occurred at the Battle of Haven.
Sun and Velvet are close friends, she notices he seemingly wants to leave Vacuo as soon as possible at the end of RWBY: After the Fall.
Sun deems Roman an enemy for attacking Blake in "Black and White". Sun later agrees to help Team RWBY in stopping Roman.
Sun has a low opinion of the organization, regarding its members as "Stupid holier-than-thou creeps" for the extreme methods they use to achieve their goals. He encountered the group twice after meeting Blake Belladonna: the first in a fight coming to her aid, the second going undercover with her to a meeting as a potential new recruit. He likely later fought against them during the Battle of Beacon, in addition to battling Grimm, AK-200s, and Paladins. During his stay in Menagerie, he is surprised to find out that there are White Fang on the island.
Sun encounters Ilia in Menagerie after catching her spying on the Belladonna household. He and Blake chase after her, and after a brief struggle, he is wounded by her. After Sun wakes up, he tells Blake that the next time he goes up against Ilia, it'll be to get even. In "True Colors", Sun fights Ilia and eventually gets the upper hand by pinning her against a pillar but stops at Blake's request. After Blake's speech, Sun pinches Ilia as payback for injuring him, showing that he is on good terms with her.
Corsac and Fennec Albain
Sun finds the Albain brothers creepy and dislikes them. While preparing to fight against the brothers alongside Ghira in "A Perfect Storm", he states that he has wanted to beat them up since the day he met them.
Sun learns about Adam Taurus from Blake and her family. After learning that he is going to assassinate Ghira and Kali Belladonna, Sun and Blake decided to fight against him and his assailants in order to not only take the White Fang back but to try and prevent them from attacking Haven Academy.
They meet in person in "Downfall", where Sun reveals to Adam saying that Blake did not come alone revealing himself along with the Menagerie Faunus, Ilia, Blake's parents and the Mistral police force leaving Adam enraged and outnumbered as his plan to destroy Haven Academy is thwarted.
In "Haven's Fate", Adam asks Sun if Blake's makes her friends fight for her, but Sun counters his claim that it's "a volunteer gig". Sun further counters Adam's claims of having lots of allies, saying that none of his followers are willing to fight for him. Angered, Adam attacks Sun, but he and Blake manage to fight him off, forcing him to retreat. Sun tries to pursue Adam, but Blake keeps him from doing so.