Izuku Midoriya is the main protagonist of the anime My Hero Academia, a superhero known by the hero name Deku. Raised primarily by his mother, Inko Midoriya, whose Quirk allows her to attract small objects, Izuku's father, Hisashi, is mentioned as having a fire-breathing Quirk but is rarely seen as he works abroad.

Born into a world where most people possess superpowers called Quirks, Izuku was part of the rare twenty percent born Quirkless, without any power of his own. Despite this setback, he never abandoned his dream of becoming a hero. He is defined by a deeply ingrained heroic instinct, a quality described as an automatic impulse to rush in and help someone in danger, even when he lacks the power to do so. This quality, combined with his timid and often tearful demeanor, makes him an unlikely aspirant, yet it is precisely this spirit that catches the attention of his idol, All Might, the world's greatest hero.

Izuku is an earnest and highly analytical individual, famously maintaining a series of notebooks filled with detailed observations about the Quirks and fighting styles of other heroes. His habit of muttering to himself while deep in thought is a common quirk of his personality. The nickname Deku, originally a derogatory term used by his childhood friend and bully, Katsuki Bakugo, meaning "useless person," is later reclaimed. A classmate, Ochaco Uraraka, reinterprets the name to sound like "Dekiru," meaning "you can do it," leading Izuku to adopt it as his official hero name as a symbol of his determination.

Izuku's primary motivation is to become a hero who saves people with a smile, just like his idol All Might. His role in the story is set in motion when All Might, impressed by Izuku's selfless bravery, chooses him as the ninth successor of his own superpower, One For All. This Quirk stockpiles enormous power and has the unique ability to be passed from person to person. After ten months of intense physical training to prepare his body, Izuku inherits One For All and gains admission to the prestigious U.A. High School for heroes-in-training.

His key relationships are central to his development. His dynamic with Katsuki Bakugo is particularly complex. Although Bakugo ruthlessly bullies him for his Quirklessness and perceived weakness, Izuku continues to admire his natural talent and drive. Their rivalry evolves from one of torment to a grudging mutual respect that pushes both of them to become stronger. He also forms strong bonds with his supportive classmates, including the kind-hearted Ochaco Uraraka and the principled Tenya Iida, who become his close friends. His relationship with Shoto Todoroki is a significant turning point, as Izuku helps Shoto confront a traumatic past and embrace his full power, demonstrating Izuku's role as an encouraging influence on his peers.

Throughout the series, Izuku undergoes substantial development. He starts as a boy who shatters his bones whenever he uses his inherited power, unable to control its overwhelming force. He gradually learns to regulate his output, developing techniques like Full Cowling to distribute a manageable percentage of One For All throughout his entire body, and later a Shoot Style that focuses on kicks to prevent further damage to his arms. As the story progresses, he awakens and learns to master the six additional Quirks that have been embedded within One For All by its previous users, including the energy-based Blackwhip, the threat-detecting Danger Sense, and the levitation ability Float. His journey is one of learning the heavy costs of being a hero, understanding that the idealistic image he once held is a burden that requires immense sacrifice. He matures from a fanboy who merely studies heroes into a strategic and decisive fighter who thinks critically about how to save everyone, including those society might deem beyond saving.