Since the beginning of the series, Tenya and Momo have been shown to share great similarities as "rich kids.". For one, both were applicated to U.A by recommendation thanks to the antecedents of their heroic families, besides that they are also considered “pretty”. Even though they don't interact too often in canon, thanks to Tenya being the class president and Momo the vice president, they are both commonly seen leading their peers and they like to teach and educate them, being strict but affectionate towards them.
They also have their respective group of friends, with Momo having Jiro and Tenya having Ochako, Izuku, and Todoroki. They both usually wear glasses, though Momo only wear them when she has to tutor her classmates in her mansion. Even if both are very applicated, Momo is very insecure with herself, with Iida is the opposite of her. The first interaction between them is at the Sports Festival, in the cavalry battle. Momo and Tenya were on Shoto's Team and Tenya was shown relying on Momo's abilities while Momo was impressed when Tenya showed her Recipro Burst against Team Midoriya and try to comfort him after Tenya felt that he almost cost his team the victory.
In the final exams, Momo and Tenya were constantly shown watching their classmates' fights against the teachers and participated in the Bakugou Rescue Squad along with Kirishima, Izuku, and Shoto. Tenya and Momo were the only ones in their Squad who refused to fight the Villains when All For One appeared and chose to save Bakugo without directly interfering in the fight. After that, they are most often seen leading their companions, as shown with the preparations for the School Festival and at the beginning of Heroes Rising when they spoke to the inhabitants of the island of Nabu for them.
In the 3rd OVA, while the students were doing their rescue training, the place in which they were suddenly trembles and this made that some rubble of the place fell down and when Yaoyorozu and Iida were investigating together, Iida grabbed Yaoyorozu and lead her to another direction for saving her with his speed quirk from the rubble that was in their direction that almost hurt Momo, hitting his head and his leg being injured by the rubble in the act and making him fall unconscious while protecting Yaoyorozu. The situation was all narrated by Momo herself to Midoriya, Ochako, and Tsuyu who made on finding Yaoyorozu and Iida after the collapsing. They then make a plan for getting out of there with Iida still unconscious, and when Momo got out with him, Tenya then wakes up and so asks about what had hapened before. She then tells him about how he did save her during the collapsing and so Iida thanks Momo for dragging him with her to outside and Momo replies back while smiling that she was very thankful to him for saving her that time.
IidaMomo fits in the lines between popular and rare-pair, but is overshadowed by ships such as TodoMomo, MomoJirou, and even IidaMei. They are often portrayed as the “class parents” due to their caring, yet parentally strict natures.
- Tenya's Relationship with Momo on the My Hero Academia Wiki
- Momo's Relationship with Tenya on the My Hero Academia Wiki