Meg Kataoka is a student at Kunugigaoka Junior High School assigned to Class 3-E, where she serves as one of the two class representatives alongside Yuma Isogai. She originally came from a higher academic track but was placed in Class 3-E after her grades dropped significantly. This decline was triggered by a classmate named Kokona, who blackmailed Meg into providing personal tutoring after Meg failed to teach her how to swim. Because Meg devoted so much time to Kokona's studies, her own performance suffered, leading to her transfer to the lowest-ranked class.

Meg is tall and known for her cool, composed appearance, which earned her the nickname Ikemegu, meaning Handsome Meg. She is highly responsible and displays strong leadership qualities, often acting as a stabilizing presence within the group. She supports Isogai in managing the class and works to keep everyone focused and motivated. Meg is respected by her peers and is particularly popular among other girls, who sometimes send her love letters. She maintains close relationships with many classmates and is seen as a reliable friend.

In terms of abilities, Meg excels in both academics and physical activities. She is the best swimmer in Class 3-E, a skill she attempts to use in an assassination plan that involves luring Koro-sensei into the pool, though the plan ultimately fails. Like all students in the class, she trains in assassination techniques under the guidance of Koro-sensei and the government instructor Tadaomi Karasuma. Her favorite subject is Japanese, while history is her least favorite. Outside of assassination training and schoolwork, her hobby is swimming.

Throughout the series, Meg grows more confident in her role as a leader and as an assassin. She participates in various class-wide schemes and helps maintain morale during difficult moments. Her development reflects the broader theme of students overcoming their personal shortcomings and learning to work together toward a shared goal.