Neptune Vasilias/Affiliation

SSSN
Neptune is a member of Team SSSN.

Sun Wukong
Neptune is good friends with his teammate Sun, and appears to have known him for some time. Sun trusts him enough to confide secrets with Neptune, even though he may not always be the best at keeping them.

Weiss Schnee
Neptune appears to take an interest in Weiss. He uses the same line as Jaune, calling her "Snow Angel," but with exponentially more success. When Team RWBY finishes planning their investigation, Neptune also seems to want to work with Weiss, as he is constantly smiling at her.

Despite Weiss herself inviting Neptune to the dance, he refused because he doesn't know how to dance and is embarrassed by it, which he later explains to Weiss. However, at the actual dance, Neptune admits that he likes Weiss even though he doesn't know her quite well and later went to approach her after being encouraged by Jaune.

However, in "New Challengers...," either unaware of Weiss' presence or despite it, Neptune attempts to flirt with the girls of Team NDGO.

Yang Xiao Long
Despite having few interactions, Neptune seems to annoy Yang, because he beat her at Remnant: The Game, and also because of his questions while at Junior's Club.

Still, while working as partners for a brief period time, they cooperate well enough to attempt to slow down the Atlesian Paladin-290. However, Neptune also compliments Yang, remarking "what a woman."

Jaune Arc
Neptune officially introduced himself to Jaune during the Beacon Dance. However, despite barely knowing each other, Neptune confessed to Jaune that his "cool guy" attitude is a facade and that he doesn't know how to dance.

After being asked to keep it a secret, Jaune encourages Neptune to approach Weiss and be honest with her instead of trying to act cool all the time. Neptune happily accepts his advice, telling Jaune that he is a really cool guy. Later, he tells Weiss that the reason why he changed his mind was Jaune, and mentions that she has a good friend looking out for her.