Nagumo is a handsome man of tall and slim build, medium-length black hair and large black eyes. He wears a red polo shirt with teal, black and white triangle-shaped patterns under a cream-colored trench coat (in the manga, the shirt is white with patterns being red and navy blue, while the shirt being light blue and the coat is brown in the digital-colored manga) as well navy-blue pants

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

Tattoos shown include:

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

1 + 1 + 1 + 1 + 1 + 1 + 1 + ⋯ {\displaystyle \phi ={\sqrt {1+{\sqrt {1+{\sqrt {1+{\sqrt {1+{\sqrt {1+{\sqrt {1+{\sqrt {1+\cdots }}}}}}}}}}}}}}} on his right forearm. This a presentation of an infinite sequence of nested square roots which resolves to ~1.6180... (the golden ratio). 5 rectangles with different designs (and the third and fifth of which are black), next to the formula tattoo. The symbols, '2', ' ϕ {\displaystyle \phi }', '1' and '%' on his index finger, middle finger, ring finger and pinky respectively. A snake coiled around his lower left leg. A swallow on the right side of his right leg, just below the knee. An impossible shape on his shin, below the swallow tattoo. A square made of various spaced lines and curves on his right thigh. A mandala-esque pattern on his right shoulder. A pair of praying hands on his left pectoral. Likely inspired by the Praying Hands drawing by Albrecht Dürer. Anton Chekhovs quote "Although you may tell lies, people will believe you, if only you speak with authority" on his right bicep[8] A line which intersect, wrapping around his anterior forearm. A patterned, isosceles triangle on his left posterior forearm. A rectangular tattoo on his right tricep. A tattoo that is a reference to Leonard Shelby from Christopher Nolan´s Memento. on his left bicep.[8] A wing on his left waist.[9] An unidentified tattoo under his left armpit.[9] Arthur Schopenhauer quote "The doctor sees all the weakness of mankind; the lawyer all wickedness, the theologian all the stupidity." on his right side.[8] A pair of hands featured in the famous painting "The Creation Of Adam" by Michelangelo, but on the tattoo what would be Adam's hand is flipped so the palm faces upwards as supposed to down.[10] Nagumo's most notable traits are his laid-back attitude accompanied by his constant smile that seems impossible to wipe off his face. He also has an incredible talent for annoying those around him to the point of making them want him dead.[11][12][13]

Nagumo also shows to had pretty carefree, even in the middle of intense battles, once claiming to enjoy the wind in his hair as he stabbed a man in the arm.[14] He is also very playful with his opponents, as demonstrated multiple times. For instance, he evades and tricks Minimalist, a hardened serial killer, before handing him some dice to decide which of his blades he'd die by.[