Nagumo tem atitude descontraída acompanhada por seu sorriso constante que parece impossível de apagar de seu rosto. Ele também tem um talento incrível para irritar aqueles ao seu redor a ponto de fazê-los querer matá-lo.
Contudo, quando se trata de assuntos envolvendo seus amigos, Nagumo tende a revelar suas verdadeiras emoções. Um exemplo disso é quando ele tira Uzuki do corte de Takamura, questionando por que o salvou, apesar de ele ser um perigoso assassino em série, influenciado pelo fato de que uma parte de Rion Akao ainda residia no corpo de Uzuki. De fato, Nagumo demonstra profundo carinho por seus antigos amigos Sakamoto e Rion desde os tempos da JAA, ainda pensando nela mesmo após sua morte ter sido confirmada. Isso também é confirmado no encontro deles durante o Arco da Exibição de Assassinos do Século , onde, assim que Rion assumiu o controle do corpo de Uzuki e falou com ele, Nagumo imediatamente reconheceu a personalidade de Rion e questionou sua identidade.

Nagumo believes that the key to killing is "deception,"[16] despite claiming to abhor it.[17]

Despite this, Nagumo possesses a colder and more serious side. He acts in his own self-interest most of the time and sometimes even commits unethical acts. When he saved Satoru Yotsumura, he blackmailed him and threatened to kill Amane if he didn't do what he wanted. Furthermore, although he didn't blackmail Heisuke (which seems to be his most common method...), he participated in the young man's kidnapping, again, to obtain information.

The tattoos shown include:

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

1
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1
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1
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{\displaystyle \phi ={\sqrt {1+{\sqrt {1+{\sqrt {1+{\sqrt {1+{\sqrt {1+{\sqrt {1+{\sqrt {1+\cdots }}}}}}}}}}}}}} on his right forearm.
This is a representation of an infinite sequence of nested square roots that results in approximately 1.6180... (the golden ratio).
An unidentified tattoo under his left armpit. [ 9 ]
Arthur Schopenhauer quotes: "The doctor sees all the weaknesses of humanity; the lawyer, all the wickedness; the theologian, all the stupidity." on his right side. [8]
A pair of hands appears in Michelangelo's famous painting "The Creation of Adam," but in the tattoo what would be Adam's hand is inverted, so that the palm faces upwards instead of downwards. [10]

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 greatest talents to ever have entered the JCC, along with Taro Sakamoto and Rion Akao, with Rion Akao acknowledging his fighting ability. Kindaka, a founding member of the Order, stated that the three could be the future leaders of the assassin world. [22] Currently, Slur considers Nagumo one of the two best fighters in the Order and therefore the second strongest assassin in the JAA. [23]

Grandma Miya stated that he is currently stronger than Taro Sakamoto due to the latter's retirement, which has lasted five years. [1] Kashima ranked him as an S-level target on the list of targets he created. [24][25] Sakamoto even stated that it would take a lot for Nagumo to lose a fight. [26] Due to his exceptional combat skills, he was able to put Gaku, one of Uzuki's strongest subordinates, on the verge of death after facing him in battle. [23]

Master of Disguise: Nagumo can perfectly copy the appearance of other people in an instant, which he used to trick Lu Shaotang into disguising himself as Sakamoto. [27] He can also disguise other people, including significantly altering someone's body shape, such as disguising the overweight Sakamoto as his wife, Aoi. When disguising Sakamoto, Nagumo says the disguise would only last twenty-four hours. [28]

Master Fighter: Nagumo's combat skills encompass everything with coordination and skill, making him a deadly fighter. [29] He can render a man completely unconscious with just his intent to kill. [30]

Nagumo is extremely proficient with bladed weapons. [ 31 ] [ 32 ] [ 33 ] [ 34 ] He was able to decapitate Minimalist with ease, [ 35 ] and kill several assassins in one swift movement before they could even react. [ 36 ]

Nagumo is a very handsome man, tall and slender, yet muscular, with medium-length black hair and large black eyes. He wears a red polo shirt with triangular patterns in teal, black, and white, under a cream overcoat (in the manga, the shirt is white with red and navy blue patterns, while in the digitally colored version, the shirt is light blue and the overcoat is brown), as well as navy blue pants (black in the digitally colored version) and black shoes.
He occasionally wears a white button-down shirt with a black tie underneath 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.