If you miss your train, then you are allowed to take the next train, but will have to take a non-reserved seat (and risk standing). You can ask JR Staff to rebook, but this will be at their discretion. You can always change seating up to 6 minutes before departure at any ticket desk.

If you miss a Japan Rail (JR) train, your options depend on the type of ticket you held. For Reserved Seat tickets, you are generally allowed to board the non-reserved (自由席, Jiyū-seki) cars of any subsequent train on the same day and for the same route without paying an extra fee. However, you will not have a guaranteed seat and must find an open spot in the unreserved carriages. If you want a new reserved seat, you will typically have to purchase a new "Limited Express" or "Shinkansen" supplement ticket, as the original reservation becomes void once the train departs. For Non-reserved tickets, you are unaffected; you can simply take the next available train within the validity period of your ticket. If you are using a JR Pass, simply go to the JR ticket office (Midori-no-Madoguchi) and ask them to cancel your missed reservation (if possible) and issue a new one for a later train; this is free of charge for pass holders. To avoid stress in 2026, always check the "JR-West" or "SmartEX" apps for real-time updates and attempt to arrive at the platform at least 10 minutes before departure.