Izuku Midoriya, also known as Deku

I'm not gonna be your worthless punching bag Deku forever... Kacchan. I'm... I'm the Deku who always does his best!
Izuku Midoriya to Katsuki Bakugo in "Rage, You Damned Nerd"

Izuku Midoriya, also known as Deku, is the protagonist of My Hero Academia.

Though born without a Quirk, he manages to catch the attention of the legendary hero All Might due to his innate heroism and has since become his close pupil as well as a student at U.A. High School. All Might passed on his Quirk to Izuku, making him the ninth holder of One For All.

Appearance

Izuku is small for his age, his round face framed by a short mess of fluffy dark green hair which sticks up at odd angles around his head, casting noticeably dark shadows onto itself. His eyes are large and somewhat circular, their irises the same green color as his hair, and are usually stretched quite wide, giving him an innocent appearance. He has a set of four symmetrical freckles in diamond formations, one on each cheek. Despite these prominent traits, he is often described as being plain-looking.

Though he was initially very skinny, Izuku has gained an array of toned muscles after his ten months of extensive training with All Might, and as the series progresses these are shown to become more developed and defined as he gradually grows stronger

After his fight with Shoto Todoroki, the fingers on his right hand became slightly deformed, and his hand shows scarring. His right arm was further damaged after his fight with Muscular, leaving various other scars all over it. Following his recovery after said fight, Izuku wears a compression sleeve on his right arm in order to support the heavy damage it sustained.

During his Junior High School days, he wore a plain black gakuran uniform with yellow buttons, accompanied by white sneakers. While at home, he wears a green jinbei over a white shirt and grey sweatpants.

At U.A., he wears the standard male uniform: a light gray blazer with dark turquoise trimmings over a white dress shirt and dress pants, along with a red tie which he doesn’t do up properly, leaving it much shorter than it should be. Instead of the plain brown shoes worn by the majority of the student body, he usually wears oversized red boots with thick white soles, laced up to the top.

Izuku's original hero costume is a green full-body jumpsuit with a red belt, elbow pads, knee pads, and gloves, along with his signature red boots. He also wears a mask with long ear-like protrusions that resembles All Might's haircut, and a respirator with a smile on it that also reflects this said hero's. The costume is severely damaged as a result of his fight with Katsuki Bakugo, and has to be repaired, meaning that during the USJ Arc and at My Hero Academia -  Save! Rescue Training, he has to wear the U.A. gym uniform. This consists of a dark blue high-collared tracksuit with thick white lines over his torso and down his legs, forming the letters “U” and “A”, and along with this, a respirator.

Izuku's second hero costume has a few changes, and now looks sturdier and more combat-ready in appearance. The knee pads have been extended to his legs and reach up to his thighs, and his new gloves are tinted beige, and are decorated with blue stripes. His respirator is now metal, diamond-shaped, and has eight holes. Izuku goes without a mask in his second suit.

During the Provisional Hero License Arc, Izuku had his costume upgraded again to suit his Shoot Style, by adding iron soles to his red boots to increase the power of his kicks. Arm braces were added, and his knee pads now have yellow bolts fastened into them. Sometime later, just before the Cultural Festival, Mei Hatsume creates support gloves to better help him use his powers for long-range attacks.

Personality

Izuku is a very timid, helpful, and polite boy, frequently overreacting to abnormal situations with exaggerated expressions. Due to being bullied for lacking a Quirk, he is initially portrayed as insecure, more reserved, and non-expressive. These traits are especially present around Katsuki Bakugo, who constantly subdued him for his aspirations to be a hero. However, after being accepted into U.A. High School, making new friends, and facing Katsuki during the Battle Trial Arc, Midoriya gradually turned into a more confident and brave person, eventually developing leadership skills.

Additionally, Izuku is quite diligent and strong-willed. His dream drove him to write down notes about everything he knows in regards to Hero's Quirks. Because of this practice, Izuku has developed a great analytical mind and can form complex battle plans in seconds, which factor in both his allies' and enemies’ Quirks. Izuku externalizes his observations through endless mumbling, a habit which annoys or scares his peers. Izuku often writes down his observations in a notebook he refers to as Hero Analysis for the Future.

Izuku is a caring person and never hesitates to rescue someone in danger, even if he knows that he is not strong enough to do it. Often, he does this on a whim, taking a more careless approach than the usual overthinking he goes through. Izuku often helps people with personal and emotional problems, even if it does not concern him, claiming that a Hero should meddle in other people's lives. Izuku's heroic spirit is recognized by many, having earned the loyalty and gratitude of characters that were previously antagonistic to him such as Tenya Iida, Shoto Todoroki, Hitoshi Shinso, Kota Izumi, and leading him to be acknowledged as a true hero by Stain.

Of all Heroes, the Symbol of Peace has impacted Midoriya's life the most, seeing as how Midoriya models himself after the former Number One Hero. Many of Izuku's decisions and actions result from his desire to become a Hero similar to All Might, and thus he has a great devotion for him, to the point of collecting several pieces of various Merchandise related to the Hero and emulating several of his traits. Having inherited his Quirk, one of Izuku's current priorities is to be able to live up to his idol's legacy, as he is always looking for ways to improve his usage of One For All, being aware of the immense pressure that is succeeding the greatest Hero of all time.

Izuku appears to have a more brash and abrasive side to him that mostly shows up when he finds himself in combat. This side of him makes him act more like Katsuki, being rather loud and unwavering, and also with a strong drive towards victory. He claims that this is because he sees Katsuki as the embodiment of what someone who strives for victory should be. He has also admitted that he doesn't like this side of him very much and tends to keep it in check.

He even shows concern for the people he deeply cares about, when he was horrified how injured Ochaco Uraraka was when he lost control of Black Whip during the Joint Training Arc and how much destruction it caused, even protected her from Hitoshi's Capturing Weapon.