Cardin is a former first-year student at Beacon Academy.
Jaune has been bullied by Cardin for weeks since class started. Cardin seems to view Jaune as weak and worthless, even stating that it would be fine by him if Jaune were to be killed by a Beowolf.
Cardin seems to enjoy tormenting Jaune as much as he has him do favors for him. As of "Forever Fall", Jaune is seen doing many favors for Cardin, such as his homework and projects, and even collecting items for a field trip to the Forever Fall forest.
During the trip to Forever Fall, Cardin attempts to get Jaune to take part in a revenge scheme targeting Pyrrha, but Jaune refuses to harm his teammate and Cardin beats him up. Even so, when Cardin is attacked by an Ursa, Jaune fights to protect him and defeats the Grimm. As a result, Cardin seems to have developed a certain respect for Jaune's abilities as a fighter.
Cardin seems to have a strong dislike for Pyrrha, calling her a "know-it-all". His dislike stems from her insulting him for his intolerance and then making a fool of him in Bartholomew Oobleck's class by then correctly answering the question he answered incorrectly. He later attempts to have her attacked by Rapier Wasps in retribution, although, the attack fails due to Jaune.
Cardin, alongside the rest of his team, would later face Pyrrha in a sparring match in preparation for the Vytal Festival tournament. Much to his growing frustration, the combined efforts of him and his team are not enough to defeat Pyrrha, and they are soundly defeated. Cardin grudgingly attributes this defeat to a "lucky shot".
Velvet is another victim of Cardin's bullying, with his team members taking part in the act. It appears their actions are motivated by her status as a Faunus.
Not much interaction has happened between Cardin and Ruby, but in Chapters 1 and 2 of the manga, Cardin insults and makes fun of her during their match.
Cardin has been doing poorly in Oobleck's class and does not appear to take it seriously. The bigotry and ignorance Cardin exhibits towards the Faunus seems to disappoint Oobleck, as he shakes his head when Cardin suggests Faunus only had an advantage in the Faunus Rights Revolution because "an animal" is easier to train than a Human. Oobleck later reprimands him and Jaune for their poor performance in his class and assigns them extra work, though Cardin later blackmails Jaune into doing the work for both of them.