Itsuka decides to let Tetsutetsu's team participate in the tournament event of the U.A. Sports Festival as her replacement, feeling that they deserve the opportunity more. They get along well, as Tetsutetsu follows her deduction of the villains being the cause of danger in the forest training camp and they go after the class.
Tetsutetsu also seems to value Itsuka's well being, as he rushes to her aid to give her his gas mask and protect her from the villains, despite his life being in danger. The two appear to be on good terms, and unlike with Neito Monoma, the two have not been seen arguing or fighting or criticizing each other, indicating that their relationship is calmer than the one Itsuka has with Neito.
Tetsutetsu has a very good opinion of Itsuka, praising not only her strategic capacity, her cheerful personality, and her positive influence on Class 1-B, but also because she is the reason that her class hasn’t descended into jealousy over Class 1-A as Neito has.
Tetsutetsu and Neito appear to be on friendly terms, and can often be seen together. Although he doesn't go along with Neito's plan to throw the qualifier in the U.A. Sports Festival, they agree there will be no hard feelings in the Cavalry Battle.
Tetsutetsu and Ibara appear to be friends. The two team up in the Cavalry Battle and partner up in the inter-class test of courage during the training camp. Tetsutetsu cares for Ibara's well being and makes sure she is safe before he goes to confront Mustard in the League of Villains' attack.
Tetsutetsu has a good relationship with his classmate Juzo. The two team up in the Cavalry Battle and Juzo wishes him and Ibara luck when they are chosen to participate in the tournament event of the Sports Festival.
Later, they team up again during the third round of the Joint Training Battle against the Class 1-A team. Right after the third set begins, Tetsutetsu begins tearing through entire structures in his search for the other team. While Sen Kaibara and Pony Tsunotori express their disagreement with Tetsutetsu's "strategy", Juzo remarks that Tetsutetsu's approach is actually playing to their team's strengths.
Tetsutetsu and Eijiro are constantly compared in the U.A. Sports Festival because of their Quirks, and eventually fight to a draw in the finals. This creates a fierce rivalry between the two that does not subside until Eijiro defeats Tetsutetsu in an arm-wrestling match. Afterwards, Eijiro offers his hand and tells Tetsutetsu he put up a great fight. Tetsutetsu accepts the handshake and gains a new respect for Eijiro.
Tetsutetsu cheers for Eijiro during his battle with Katsuki Bakugo and is upset when he loses. They later intern together (by a stroke of luck) with Fourth Kind, and appear to be happy to do so together.
Tetsutetsu despises Katsuki's arrogance. He has stated a desire to want to defeat Katsuki but has not been presented with an opportunity to do so as of now. When Eijiro fights Katsuki during the U.A. Sports Festival Finals, Tetsutetsu roots for Eijiro to beat him. He is shocked to see Katsuki not only win the fight but also become the winner of the entire festival.
Tetsutetsu fights Shoto during the third round of the Joint Training Battle. Tetsutetsu decides to take Shoto on because his Quirk, Steel makes him resistant to Shoto's Half-Cold Half-Hot Quirk, and also because Shoto is a recommended student and Tetsutetsu, therefore, sees him as an obstacle to overcome.
Both take their Quirks to their limits in order to defeat the other. Although the heat produced by Shoto’s flames begins to affect Tetsutetsu, he continues his brutal assault against Shoto, deriving his combat to a battle of endurance. However, both Tetsutetsu and Shoto end up unconscious from the confrontation and wake up in the infirmary.
Although the round ends in a draw, Tetsutetsu feels like he has lost and tells Shoto that he would like to have a rematch in the future. Despite the wildness of their fight, none holds a grudge against the other.