On his first day of junior high, Eren Yeager comes face-to-face with a titan—and has his lunch stolen! From that day on, he holds a grudge against titans for taking his favorite food from him, a cheeseburger, vowing to eliminate their kind once and for all. Along with his adoptive sister Mikasa Ackerman and their friend Armin Arlert, the trio traverse the halls of Titan Junior High, encountering familiar faces and participating in various extracurricular activities as part of the Wall Cleanup Club.

A parody of the immensely popular parent series, Shingeki! Kyojin Chuugakkou places beloved characters as junior high school students, fighting to protect their lunches from gluttonous titans.

The seemingly unimpressive Saitama has a rather unique hobby: being a hero. In order to pursue his childhood dream, Saitama relentlessly trained for three years, losing all of his hair in the process. Now, Saitama is so powerful, he can defeat any enemy with just one punch. However, having no one capable of matching his strength has led Saitama to an unexpected problem—he is no longer able to enjoy the thrill of battling and has become quite bored.

One day, Saitama catches the attention of 19-year-old cyborg Genos, who witnesses his power and wishes to become Saitama's disciple. Genos proposes that the two join the Hero Association in order to become certified heroes that will be recognized for their positive contributions to society. Saitama, who is shocked that no one knows who he is, quickly agrees. Meeting new allies and taking on new foes, Saitama embarks on a new journey as a member of the Hero Association to experience the excitement of battle he once felt.