The friendship began when Izuku met Tenya and Ochako in the U.A. Entrance exam, first admiring their powers and later saving Ochako from one of the test robots, earning respect from Tenya and growing close to both of them after they became classmates. They are regarded as the "Original Dekusquad" and are Izuku's closest friends. Ochako is revealed to have some high school crush on Izuku in Season 3 in the Provisional Hero License Exam Arc, and took Izuku as one of her main inspiration so far in UA. Tenya also took Izuku and his brother, Tensei as one of his main inspiration so far in UA. Izuku and Ochako both are worried for Tenya after they recieved the news about his brother getting heavily injured because of the Hero Killer, Stain. In the Tartarus Escapees Arc, Prior to Class 1-A's showdown against Izuku, it is revealed that the students confronted Endeavor about Izuku's location after receiving his farewell letters and, although at first they are surprised, Tenya and Ochako are among the most willing members of the Class to help and recover Izuku. Both Tenya and Ochako has holds Izuku's hand. First is when Tenya reach out to Izuku, second is Ochako when the civilians telling Izuku to get out, and third is Tenya hold Izuku's hand when Izuku meet Inko. In OVA 1: Save! Rescue Training, it's shown that both Tenya and Ochako are protective about Izuku, they're angry at All Might for Izuku.
Shoto “joined” the Dekusquad following the U.A. Sports Festival Arc, after he got over his one-sided rivalry with Izuku and came to terms with his quirk as well as his father, which was the source of most of his antisocial behavior. In addition, when Izuku sends out his location during the fight with Stain in the V.S. Hero Killer Arc, Shoto is the first and only one to come to his aid, stating to his father that his friend is in trouble. After this, he is shown to open up to his classmates more and is often seen eating with Izuku and his friends. He, Izuku and Tenya are in the Bakugou Rescue Squad in the Hideout Raid Arc. He and Izuku became close, in fact, he invited both Izuku and Katsuki to do their hero work study in his father's agency so they go on the same missions together in the Movie 3: World Heroes Mission. He were also in a good terms with Ochako, in Movie 1: Two Heroes, after he, Eijiro and Katsuki saved her, he is the only one who asked is she okay. In the Tartarus Escapees Arc, both are on the Evacuation Team to evacuate and protect civilians and are the ones who show the most concern when Izuku and Katsuki leave the group to join the Heroes' battle against Tomura. When Ochako is giving his speech for the civilians to let Izuku enter U.A. after the disaster of the war, Shoto was shown listening intently to his speech along with Endeavor and Keigo. In BNHA Smash, Shoto once expressed worry for Ochako and gave her something to make her feels better after puking.
During the USJ incident, Izuku and Tsuyu were forced to fight off villains together, and showed commemorable teamwork in defeating them. In addition, when the Bakugou Rescue Squad recruits Deku for their mission, Tsuyu doubts their plan and tries to convince them not to go, stating that they would be “no different than villains”, however, they ignore this statement, and go on the rescue mission anyways. Tsuyu later feels bad about doubting them, which leads to both parties apologizing once the mission is over and thus repairing their friendship.
There is controversy to whether Tsuyu actually belongs in Dekusquad, but she's widely accepted to be a member as she is shown eating and hanging out with the group multiple times. In some fanworks other characters are added to this group such as; Hitoshi, Yuga, Momo, Toru, and less often, Fumikage, and lesser, Minoru. However, they are not actual members of the canon.
The group was also dubbed and is sometimes referred to by fans as the "Deku Squad" or "Izucrew."
The alternative, or rival, group is the Bakusquad, which consists of Katsuki Bakugou, Eijiro Kirishima, Denki Kaminari, Hanta Sero, Mina Ashido and occasionally Kyoka Jirou. There's no canon rivalry between the two groups, but the rivalry between their namesakes Deku and Bakugou is enough for the fandom to support the idea. They are opposites in the tone of their friendships, as Dekusquad is more calm and controlled and Bakusquad is loud and chaotic.
- DekuTsuChako refers to the ship between Izuku, Tsuyu and Ochako
- IidaOcha refers to the ship between Ochako and Tenya
- IidaDeku refers to the ship between Tenya and Izuku
- IiTsuyu refers to the ship between Tenya and Tsuyu
- IiTsuChako refers to the ship between Tenya, Tsuyu and Ochako
- IzuOcha refers to the ship between Izuku and Ochako
- MidoTsuyu refers to the ship between Izuku and Tsuyu
- OchaIiDeku refers to the ship between Ochako, Tenya and Izuku
- TodoChako refers to the ship between Shoto and Ochako
- TodoDeku refers to the ship between Shoto and Izuku
- TodoIida refers to the ship between Shoto and Tenya
- TodoIiDeku refers to the ship between Shoto, Tenya and Izuku
- TodoIiDekuOcha refers to the ship between Shoto, Tenya, Izuku and Ochako
- TodoIzuOcha refers to the ship between Shoto, Izuku and Ochako
- TodoTsuyu refers to the ship between Shoto and Tsuyu
- TsuChako refers to the ship between Tsuyu and Ochako