Seishiro is an incredibly tall man, being visibly taller than nearly all of his teammates. Seishiro has short white hair that leaves a V-shaped fringe in between his eyes. He has gray-colored eyes with large irises. Seishiro currently plays as a rightwing for England's Manshine City in the Neo Egoist League. After the Blue Lock Eleven played against the Japan U-20 team, Nagi ranked as one of the top players in the project.