𝓝ᥲgі 𝓢ᥱіsһіr᥆ ꪆ୧

Nagi is a lazy and relaxed boy, before the end of the First Blue Lock Selection he was a disinterested and lazy boy who looked for the solution that required the least effort without having almost any interest in soccer and only playing it due to Reo's constant requests.

Nagi is a remarkably tall teenager. He has white hair that forms a V-shaped fringe between his eyes, like Isagi. He has gray eyes with large irises. In Blue Lock, Nagi wears the standard uniform (black with blue stripes) and tracksuit. During the First Selection for the V Team, he wore the number 11. During the Second Selection for the White Team, the Third Selection for the C Team, and the match against the Japanese U-20 National Team, he wore the number 7. During the Neoegoist League for Manshine City, he has returned to wearing the number 11. In high school, Nagi wore a school uniform consisting of a white sports jacket with a cascading star pattern at the collar, though underneath he wore a dark hoodie instead of a dress shirt and tie. He also wore dress pants and dress shoes.

Seishiro Nagi (凪なぎ 誠せい士し郎ろう, Nagi Seishirō) is the protagonist of the spin-off Blue Lock Episode Nagi. He is an aspirant of the Blue Lock project and currently plays as a right winger for the English team Manshine City of the Neoegoist League. In his match against Team X in the First Selection, Nagi began to show signs of his "passion" as he had to really put in the effort to win.