Itsuka and Neito are friendly towards one another and can often be seen with each other. However, she does not approve of Neito's constant mockery of Class 1-A. Whenever he decides to taunt them for whatever reason, Itsuka will step in, knock him out and apologize for his actions. Although Itsuka criticizes Neito quite heavily, Neito never seems to have any animosity, indicating the friendly atmosphere between them. She also seems to enjoy teasing Neito. She turned him in during the scavenger hunt for being a perverse person and taunted him about making enemies with Katsuki while patting his head. It is revealed she shares his dislike for being upstaged by class 1-A.
Itsuka decided to let Tetsutetsu's team participate in the tournament event of the Sports Festival as her replacement, feeling that they deserved the opportunity more. She notes that Tetsutetsu is aggressive and overzealous, but does not seem to think that these are necessarily bad things. This was seen when they go after the villain Mustard, as Tetsutetsu voiced that he will protect the class, Itsuka notes while he has a one-sided mind, his intentions are good. She smiled and agreed with his declaration, showing she respects him.
Tetsutetsu also seems to value Itsuka's well being as he rushed to her aid to protect her. The two appear to be on good terms, and unlike with Neito, the two have not been seen arguing or fighting or criticizing each other, indicating that their relationship is calmer than the one she has with Neito.
Kendou and Reiko are good friends. Reiko was was the one who designed her outfit for the Beauty Contest, and helped her to prepare for the competition. They also interned at the same place.
Itsuka and Momo interned together under Uwabami. Although they were treated like Uwabami's entourage during their time together, Momo always tried to find a lesson in everything. Itsuka appeared to feel sorry for Momo, seeing that she was clearly in denial.
However, the two were shown to get along, despite them being from different classes.
Months later after their internship with Uwabami, she and Momo were continued to be treated as a pair by fans. Even though she did not show it, she could not stand being continuously compared to her because the latter had better grades and a better quirk. She tells Momo about these feelings before the second round of the Joint Training Battle begins and in addition says that she has been waiting to duke it out with her for a while. Despite ultimately winning the second round for Class 1-B, she is not satisfied and says that it did not feel like she actually won as she gazes upon an unconscious Momo.
Even with her self-declared rivalry with Momo, Itsuka still accompanies her to the infirmary while looking concerned. This goes to show despite their rivalry, its a friendly one.