UA Academy's Class 1-A has been the focus of a substantial amount of public attention due to the multiple villain attacks they have faced over the past school year. This attention has left Class 1-A's rivals, Class 1-B, feeling quite bitter. Desiring to prove their skills, they look forward to the opportunity that has been given to them: a set of mock battles between the students of each class. The classes are split into squads of four, each of which is tasked with capturing the other group members. The winner is the group who first secures all of the opposing team. While this sounds simple, a curveball is thrown into the mix with the inclusion of General Course Student Hitoshi Shinsou, who wishes to transfer into the Hero Course. Despite using his training with Class 1-A's homeroom teacher Shouta Eraserhead Aizawa to prove that he's capable of being a real hero, he is still far behind the others due to his lack of experience. However, Shinsou is determined to overcome this challenge. Thus begins the fiery competition between Class 1-A and 1-B as each tries to prove that they are superior to the other.

As summer arrives for the students at UA Academy, each of these superheroes-in-training puts in their best efforts to become renowned heroes. They head off to a forest training camp run by UA's pro heroes, where the students face one another in battle and go through dangerous tests, improving their abilities and pushing past their limits. However, their school trip is suddenly turned upside down when the League of Villains arrives, invading the camp with a mission to capture one of the students. Boku no Hero Academia 3rd Season follows Izuku Deku Midoriya, an ambitious student training to achieve his dream of becoming a hero similar to his role model—All Might. Being one of the students caught up amidst the chaos of the villain attack, Deku must take a stand with his classmates and fight for their survival.

Episode 1: HLB HLB stands for Hero League of Baseball—it is a baseball league founded by pro-heroes who love baseball! It's game day! The last game of HLB championship is between Gang Orca and Shishido's two rival agencies. They form a team (Orcas and Lionels) to compete. In the world of HLB, there is no rule—using their Quirks is of course accepted; however, just when the game is about to finish, they are interrupted by a villain. Who will be the winner of HLB?! Episode 2: Laugh! As if you are in hell Deku, Bakugo, and Todoroki participate in an internship under the No.1 hero, Endeavor's agency. One of their tasks these days is to find a villain (Smiley) who draws doodles in the city; however, since the urgency is so low, they let other pro-heroes solve this case. One day, Smiley draws a doodle on Endeavor's house! Being furious, Endeavor himself and the 1-A trio go out to get the villain' however, Smiley's Quirk turns out to be something ridiculous but powerful... It is to make anyone who looks into his eyes laugh hysterically! Can the team capture the villain and stop laughing?!

Returning from their internships, the students of Class 1-A are immediately thrown into more training by their homeroom teacher, Shouta Aizawa. For this exercise, the class will be joining four students from Isamu Academy High School to compete in a survival game. Split up into groups of four, students must either eliminate each other or stay hidden until time runs out to win. The training also acts as a reunion between Tsuyu Asui and her friend from middle school, Habuko Mongoose. However, not all the students from Isamu are friendly—Katsuki Bakugou almost instantly picks a fight with Romero Fujimi. The conflict between the two leads Romero to angrily release his Quirk, a gas which zombifies anyone it comes in contact with. How will the remaining students deal with the situation after most of the people around them turn into zombies?