Shinkansen oversized luggage rule in 2026 — when does a normal suitcase need a special reserved seat, and how is it actually booked?
Since 2020 the Tokaido, Sanyo, and Kyushu Shinkansen lines have required a free advance reservation for any bag over 160 cm (sum of length+width+height); boarding without one triggers a ¥1,000 penalty and a forced relocation of the bag. Standard 28-inch / 32-inch tourist suitcases routinely cross that 160 cm line, but most international guides still don't mention the rule and visitors learn about it at the conductor's hand. Which seat numbers actually pair with the oversized luggage area, how is the reservation made (smart-EX, JR ticket window, or paper agents), and what counts as exempt (instruments, sports gear, strollers)?