Tenya has a very good relationship with his older brother, Tensei. Tenya looks up to Tensei and sees him as a role model, aspiring to be like his older brother. When Tenya found out that Tensei was critically injured, he left the Sports Festival (despite knowing he could receive a medal) and rushed to see his brother in the hospital. The bond between them is so strong that Tenya decided to avenge his brother by seeking out Stain, the villain who ended Tensei's hero career. Tensei also has great respect for Tenya, calling him a "brilliant little brother" and apologizing to him for failing to live up to his expectations as his role model.
At their first meeting, Tenya thought that Izuku was an annoying person who couldn't keep silent in the entrance ceremony. He later reprimanded him in making light of the prestige of UA, which earned Izuku mockery from the other students. After observing him during the Entrance Exam, though, Tenya was greatly impressed by Izuku's heroic actions when Izuku saved Ochaco instead of focusing on himself in the test.
When they met again, Tenya apologized for his previous judgment in Izuku as he believed that Izuku had some kind of intuition that he himself lacked. Along with Ochaco, Tenya was one of the first people to befriend Izuku on their first day of school. Although he greatly respects and admires Izuku, he also views him as a rival; Tenya feels that he needs to challenge him in order to grow as a hero. However, the rivalry between them is much friendlier than Izuku's other rivalries. Tenya respects Izuku for his dedication towards a goal or task once he has put his mind to it and not giving up on said goal or task. Izuku likewise respects Tenya's leadership, determination, and perseverance.
Since they're both friends with Izuku, they became friends with each other too. Tenya and Ochaco both mutually care for each other's well-being, and both expressed concern when the other was put in harm's way. The two seem to trust each other a great deal and work well together as a team, although they did find themselves on opposite sides during the UA Sports Festival's Cavalry Battle. During the Cavalry Battle Tenya surprised Ochaco with Recipro Burst with Ochaco playfully pestering Tenya for concealing his abilities which caused Tenya to profusely apologize. Tenya like most of Class 1-A is also accustomed to Ochaco's usual cheery demeanor and as such became somewhat unnerved by Ochaco's determination for the then upcoming UA Sports Festival. Tenya along with Izuku are the only two students Ochaco was comfortable sharing her reasons for wishing to become a hero with and Tenya like Deku believes that Ochaco's goal is a noble one, with Tenya believing that there was no shame in her quest for wealth even before discovering it was due to Ochaco's wish to better her parent's lives.
Because of their equally forceful personalities and very different personal values, Katsuki and Tenya don't get along well. Katsuki looks down on Tenya's privileged background and dislikes being ordered around by him, whereas Tenya disapproves and frequently reprimands Katsuki for his improper behavior, questioning his intentions to become a hero. This was especially apparent when they were forced to partner up for the Trial of Battle.
Despite their bad standing, Tenya joined some of his classmates in saving Katsuki from the League of Villains. It is unknown what sort of standing they have now since this experience.
Manual sent in a nomination for Tenya because he felt he could relate to him on some level. Tenya only accepted the nomination in order to search Hosu for the Hero Killer, and his grave aura made Manual slightly uncomfortable at first. Tenya ignored Manual's warnings against pursuing vengeance and was scolded for it after the incident. In the end, Tenya promised not to make the same mistake again, so they're not on bad terms.
Tenya is usually the first to chastise Minoru for being an unabashed pervert. Minoru, in turn, views Tenya as a killjoy and a prude.
Tenya and Shoto get along well. During the Stain incident, they cooperated and defended each other, and Shoto called out to Tenya with strong words to set him on the right path.
The two were partnered up during the final exams against power loader. The were shown to work and get along well. During the exam the show showed trust in each other as they used the combined power of their quirks to throw Ojiro through the gate resulting in the two passing.
Tenya despises Stain, the villain who severely injured his older brother Tensei. Tenya sought out Stain in Hosu during his workplace experience and confronted him in a rage. Stain regarded Tenya first as a child in a suit, then as a foolish example of the kind of false hero he was trying to purge.