Top sushi-ya have 1–10 seats. Reservations are essential, sometimes months ahead. Use a concierge or specialized booking service.
Mid-range and standing sushi (sushi tachigui) often accept walk-ins. Try Standing Sushi Bar Uoshin or Tomoe Sushi.
Don't be late — even 5 minutes can cause the chef to refuse the reservation. Punctuality is sacred.