Eijiro has spiky red hair that resembles horns (which is not its natural appearance) and a little scar above his right eye that can be mistaken as a single long eyelash. Despite his young age, Eijiro possesses an impressive physique and a muscular body.
In his middle school days, Eijiro's hair was black and not spiked. He changed it to his current style shortly after being accepted into U.A.
In his costume, he wears a vest that consists of two shoulder pads that are shaped like gears that wrapped around his shoulders while his chest is left uncovered, and wears a skirt with a ripped pattern over pants with an "R" belt. He also wears a mask that somewhat resembles the same mask that the main character of Akumetsu wears. His costume looks like an Aka Oni (red troll-like creature). During the Hero License Exam Arc, his costume gains long crimson sleeves.
Eijiro is a very boisterous, outgoing guy with a fondness for the concept of manliness, often using the terms "manly" and "unmanly" to describe stuff he does or doesn't like. Those who showcase a noble, brave or determined attitude tend to emotionally move him to tears, quickly earning his complete admiration, respect and friendship. Similarly, he will call out traits that are the opposite of that, such as cowardice and dirty play. He is also a big fan of Crimson Riot, a retro hero that he takes inspiration from, including his own hero name.
Eijiro is honest and kind-hearted, with All Might praising his heroic spirit. In addition, he seems capable of making friends with most people, as he is one of the few classmates who is friends with both Katsuki Bakugo and Izuku Midoriya. Eijiro is very dedicated to his friends and is even willing to break the law and the rules in order to help them, showing regret if he becomes unable to do so.
Eijiro has stated more than once that he does not think very highly of his own Hardening Quirk, thinking that it lacks the flashiness usually found in the Pro Hero scene. In fact, he will get downright offended if he finds someone with a similar Quirk. Eijiro also voices his concerns about not having a good enough Quirk to Kaminari, Tokoyami and Bakugo, worried that his skills could not compare to the others. A lot of this self-doubt seems to have come from an incident in Junior High, when Eijiro saw Mina stop an underclassman from being bullied and save some students from a threatening figure. Eijiro's friends pointed out that Mina will easily become a hero due to her outgoing personality and athletic nature. After this, Eijiro thought of himself as dull and boring.
Regardless, in the present, Eijiro is a more confident and hot-blooded fighter, although not to the same degree as Katsuki. However, he does not shy away from comparing himself to Katsuki, with Izuku stating that the two have managed to develop a relationship between equals. Because of this, Eijiro is notably one of the few people that Katsuki holds some respect for.
When he was three years old, he was in bed and woke up since he had to go to the bathroom. When he rubbed his eye, his Quirk manifested for the first time. This made his hand harden and caused Eijiro to cut himself, which left a scar on his right eye.
During Junior High, Eijiro and Mina attended the same school and although they were not close, Mina's outgoing nature and strong personality made Eijiro self conscious of his own appearance and personality.
Quirk and Abilities
Hardening (硬化 Kōka?): Eijiro's Quirk gives him the power to harden and sharpen any part of his body. The ability not only protects him from physical attacks, but also from heat and shock waves. The drawback to his Quirk is that there is a limit to how much damage the hardened skin can withstand and will cause the hardening to slowly dissipate.
- Red Counter (
烈怒交吽咤Reddo Kauntā?): While hardened, Eijiro endures a close-range attack with his skin, and then counters with a straight punch.
- Red Riot Unbreakable (
烈怒頼雄斗 安無嶺過武瑠Reddo Raiotto Anbureikaburu?): Eijiro reaches his maximum hardening level by turning his entire body extremely hard and rugged, leaving him with a monstrous appearance and practically invulnerable to most forms of attack. This form can only be maintained for around 30 to 40 seconds.
- Red Gauntlet (
烈怒頑斗裂屠Reddo Gantoretto?) Eijiro rushes towards the enemy and delivers a single strong punch against them.
Enhanced Strength: While using his Quirk, Eijiro's physical strength appears to increase. He demonstrated it multiple times during the Sports Festival, first digging through several tons of metal scraps, then withstanding Katsuki's explosions without stumbling, which, according to the latter, was not due only to Eijiro's armor. In his arm-wrestling match against Tetsutetsu, his fingers dug through concrete and he eventually broke the surface the match was taking place on. He was also able to break multiple metal blades with a single elbow strike, as well as to destroy a wall with Izuku's help.
Enhanced Durability: Eijiro has enhanced durability thanks to his Quirk. His Hardening was able to withstand Katsuki's explosions for an extended amount of time and allowed him to emergence from the remnants of the huge faux villains that fell on top of him completely unscathed.
- He is student No. 8 in Class 1-A.
- He ranked 2nd during the Entrance Exam and 8th during the Quirk Apprehension Test.
- His rankings in the Popularity Polls are as follows:
- He ranked 15th in the First Popularity Poll.
- He ranked 5th in the Second Popularity Poll.
- His name contains the kanji for cut (切?) and sharp (鋭?).
- He likes meat and manly things.
- Horikoshi mentions that Eijiro was made to tie the class together with his personality.
- He ranks 15th in Class 1-A's Grades.
- Eijiro ranked in the Top 8 of the U.A. Sports Festival First-Year Stage.
- (To his classmates about Katsuki Bakugo's kidnapping) "When I heard that they were after my buddy...I couldn't do anything!! I didn't do anything!! If I don't act now...forget being a hero, I'm not even a man!"