Izuku Midoriya, also known as Deku is the main protagonist of the My Hero Academia manga and anime series. Even though Izuku was born Quirkless, he manages to catch the attention of the legendary hero All Might due to his innate heroism and a strong sense of justice, and has since become his close pupil, as well as a student in Class 1-A at U.A. High School. All Might passed on his transferable Quirk to Izuku, making him the ninth holder of One For All. Following the Paranormal Liberation War, with Tomura Shigaraki and All For One actively targeting Izuku for his Quirk, he decides to leave U.A. before finishing his first year to keep his classmates out of harm's way. After encouragement from his friends, he later returns to the school and leads the heroes against the villains in one final, desperate battle to save the world. Izuku's greatest asset prior to receiving his Quirk was his vast knowledge of fundamental hero skills and tactics. Izuku studied Pro Heroes for years and is able to apply that knowledge during crisis situations in a practical manner. His immense bravery and desire to become a hero were also important factors in giving him the mentality to protect others. Before gaining his Quirk from All Might, he took on the Sludge Villain and rescued Katsuki because of his boldness and application of heroic skills, something that deeply impressed the No. 1 Hero. Upon training with All Might, Izuku inherited One For All from him and was granted the ability to harness a stockpile of powerful energy.
He can move faster than the eye can see and take down an enormous villain bot in a single punch, but the physical backlash at the time prevented Izuku from being able to fight properly or compete with his peers on an even playing field. Even so, he still possessed impressive physical durability, and his drive allowed him to withstand the drawbacks of One For All for the most part. Despite the intense drawbacks of One For All, Izuku's wits provide him with ways to use One For All that is still effective in battle. He also retains his ability to act instinctively based on his notes and possesses basic hand-to-hand combat knowledge. By applying those correctly, Izuku is able to fight toe-to-toe with even the strongest students of Class 1-A, such as Katsuki and Shoto. Under the tutelage of Gran Torino, Izuku acquired more control over One For All, leading to the creation of One For All: Full Cowl, a technique that would eventually become a key component of his fighting style. With Izuku gaining greatly enhanced maneuverability, strength, and a significant reduction in the physical backlash created when using his Quirk uncontrollably, he was able to drastically improve his overall fighting capabilities; his newly attained abilities garnered praise from Gran Torino, who noted that Izuku was on a higher level than he was compared to the Sports Festival. This specific improvement enabled Izuku to compete more closely with his classmates in the physical aspects of the Hero Course and even allows him to fight properly against top villains like the Hero Killer: Stain, who had single-handedly bested various Pro Heroes. As Izuku's mastery over his Quirk improves, so do his practical skills. Also, when his skills and experience increase, so does his confidence, which is said to be a source of inspiration to his classmates as well. His body, however, still remains relatively vulnerable to One For All's drawbacks, which gives Izuku a disadvantage against enemies like Muscular or Overhaul, whose Quirks were proven to be too powerful against One For All's weaker outputs, forcing scenarios where Izuku had to sacrifice his body in order to go all out. In order to protect his own body, particularly his arms, Izuku eventually develops his own unique fighting style, diverging himself further from All Might's. Currently, Izuku is acknowledged by his classmates as a strong, reliable, leading figure, with both his strength and intelligence being respected equally. However, Izuku's Quirk is still an enigma for them (including Izuku himself), which makes him an unpredictable ally for better or worse. As Izuku keeps growing, so does One For All, and with the prospect of having new abilities unlocked in the future, Izuku has to work even harder in order to fully dominate the Quirk that was passed to him. By the time of the Paranormal Liberation War, Izuku's skills have grown exponentially to the point that he is able to fight alongside exceptional Pro Heroes such as Eraser Head, Gran Torino, and even the current number one Pro Hero, Endeavor. But his biggest feat thus far is holding his own against the Grand Commander of the Liberation Front, Tomura Shigaraki, who is powered by All For One and a modified body with strength comparable to All Might, and forcing the all-powerful villain on the defensive despite the latter easily overpowering the top Pro Heroes. Following the aftermath of the Paranormal Liberation War, Izuku has displayed greater mastery over his Quirks and showcased the ability to easily outmaneuver his enemies with Blackwhip and 45% of One For All, detect danger without gaining sensory overload, prove En wrong by creating a new Super Move using Smokescreen, and easily alternate between his arsenal of Quirks in his fight with Lady Nagant. In his fight against Class 1-A, Izuku displayed himself to be easily capable of fighting on even terms with some of U.A. High School's most powerful students and was shown capable of completely dominating them even when severely outnumbered before succumbing to exhaustion and stress. One For All Transferred to him from Toshinori Yagi, Izuku's Quirk allows him to stockpile an enormous amount of raw power, allowing him to significantly enhance all of his physical abilities to a superhuman level. This results in unbelievable levels of strength, speed, stamina, agility, and durability. Izuku can focus the stockpiled power into a single body part, or spread it across his entire body evenly, though, focusing the power in a single part puts a greater strain on that part of his body. He is also able to control what percentage of his full power that he uses. He is currently able to handle 45% of his full power without breaking his bones, with 30% being his normal output.[11] When Izuku activates One For All, red, vein-like lines course throughout the empowered part of his body. The Quirk factors of the previous power holders have merged with the core of One For All and have drastically increased in strength since. This grants Izuku the ability to access and utilize the Quirks of the previous holders of One For All. He can even use more than one of these assimilated Quirks at a time, granting him even more options in battle. Izuku also has access to a subconscious realm where vestiges of the consciousnesses of the previous One For All holders dwell. These vestiges can trigger Izuku to activate One For All without any conscious input from himself, as seen when he was under the control of Hitoshi's Brainwashing Quirk and illusionary shadows of these echoes appeared in his vision. Izuku currently has little to no control over this aspect of One For All, being unable to freely enter or exit, his body not being fully materialized, which limits his movement within the realm, and only being able to talk through muffled sounds since his mouth has not fully manifested yet. However, Izuku has reached the point where he can freely communicate with the vestiges of the previous users while still conscious. Izuku is the first holder of One For All known to have gained access to this realm while still alive.