If you miss your reserved Shinkansen (bullet train) in 2026, the rules are surprisingly flexible but specific: your ticket remains valid for non-reserved seating (Jiyuseki) on any subsequent train of the same type (e.g., Nozomi, Hikari, or Kodama) on the same day. You do not need to visit a ticket office; you can simply proceed to the platform and board one of the non-reserved cars (usually cars 1–3). However, you forfeit the "reservation fee" you paid for your original seat. If you want to secure a new reserved seat on a later train, you will have to pay the limited express reservation surcharge again at a ticket machine or counter. A major exception to this rule is the "Hayatoku" (early bird) discounted tickets, which are often tied strictly to a specific train; if you miss a Hayatoku-fare train, your ticket may be completely void, requiring you to purchase a full-price ticket. To avoid any issues, if you realize you are going to be late before the train departs, you can change your reservation for free once at any JR ticket office or via the official "Smart-EX" app.