Overall Skill Level: Nagumo is a former member of the Order and one of the strongest assassins in Japan. [21] As a student, Nagumo was one of the three top prospects to enter the JCC along with Taro Sakamoto and Rion Akao, who recognized his fighting ability. Kindaka, a founding member of the Order, stated that the three could be future leaders of the assassin world. [22] Currently, Slur considered Nagumo one of the two best fighters in the Order and thus the second strongest assassin in the JAA. [23]

Granny Miya stated that he is currently stronger than Taro Sakamoto due to the latter's five-year retirement. [1] Kashima classified him as an S-rank target on the blacklist he created. [24][25] Sakamoto has even stated that Nagumo would have a hard time losing a fight. [26] Due to his exceptional combat skills, he was able to bring Gaku, one of Uzuki's strongest subordinates, to the brink of death after engaging him in battle. [23]

Master of Disguise: Nagumo can copy other people's appearances perfectly in an instant, which he used to fool Lu Shaotang by disguising himself as Sakamoto. [27] He can also disguise others, even significantly altering someone's form, such as disguising the fat Sakamoto as his wife, Aoi. When disguising Sakamoto, Nagumo claims that the disguise would only last for twenty-four hours. [28]

Master Combatant: Nagumo's combat skills include everything from coordination and dexterity, making him a deadly combatant. [29] He can render a man completely unconscious with his killing intent alone.

Nagumo is extremely skilled with bladed weapons. He was able to decapitate Minimalist with ease, and kill multiple assassins in one swift motion before they could react.

Nagumo's most notable traits are his laid-back demeanor, accompanied by a constant smile that seems impossible to erase from his face. He also has an incredible talent for annoying those around him to the point of making them wish for his death.

Nagumo is also shown to be quite carefree, even in the midst of intense battles, once claiming to enjoy the wind in his hair while stabbing a man in the arm. He is also very playful with his opponents, as shown multiple times. For example, he evades and outsmarts Minimalist, a hardened serial killer, before handing him some dice to decide which of his swords he would die by. Another example is during his fight against Gaku, where he asked the latter if he liked Bruce Lee after receiving a one-inch punch.

However, when it comes to matters involving his friends, Nagumo tends to reveal his true emotions. One such example is when he pulls Uzuki from Takamura's cutting line, wondering why she saved him despite him being a dangerous serial killer, influenced by the fact that a part of Rion Akao still resided in Uzuki's body. In fact, Nagumo has shown deep fondness for his old friends Sakamoto and Rion since his time in the JAA, still thinking about her even after her death was confirmed. This is also confirmed in their encounter during the Century Arc Assassin Exhibition, where, once Rion took control of Uzuki's body and spoke to her, Nagumo immediately recognized Rion's personality and questioned her identity.

Nagumo believes the key to killing is "deception", despite claiming to abhor it.

Despite this, Nagumo possesses a colder and more serious side. He acts according to his own interests most of the time, and sometimes commits acts that are unethical. When he saved Satoru Yotsumura, he blackmailed him.

Nagumo is a tall, thin, and attractive man with medium-length black hair and large black eyes. He wears a red polo shirt with teal, white, and black triangular patterns under a cream-colored trench coat (in the manga, the shirt is white with red and navy patterns, while in the digital version, the shirt is light blue and the coat is brown), navy blue pants (black in the digital version), and black shoes.

He occasionally wears a white button-down shirt with a black tie under a black suit (dark green in the manga) (in which he sometimes omits the suit and tie). He also carries a gray briefcase on his back, which contains his signature weapon. [ 7 ]

At 14, Nagumo already appeared taller and thinner before reaching adulthood. His attire typically consists of a black T-shirt under a yellowish-orange jacket with black chain designs, navy blue shorts, and wooden sandals.

Nagumo has many tattoos, most of which are hidden by his clothing. His tattoos have mathematical inspirations, particularly referencing the Golden Ratio.

Tattoos shown include:

On the left side of his neck, he has a Fibonacci spiral mark. The growth factor of the Fibonacci spiral is the golden ratio, ~1.6180. Two rectangular tattoos on both hands, another reference to the golden ratio. The formula ϕ

1 + 1 + 1 + 1 + 1 + 1 + 1 + ⋯ on his right forearm. This is a presentation of an infinite sequence of nested square roots that solves in ~1.6180... (the golden ratio). 5 rectangles with different designs (the third and fifth of them are black), next to the formula tattoo. The symbols, '2', ' ϕ {\displaystyle \phi}', '1' and '%' on your index finger, middle finger, ring finger and pinky finger respectively. A snake s