In 2026, whether you need to buy train tickets in advance in Japan depends on your travel timing and group size. For standard Shinkansen travel on the Tokaido line (Tokyo-Osaka), you can often "show up and go" using unreserved seats, as trains depart every few minutes. However, for a premier experience during peak seasons like Golden Week (late April), Obon (August), or New Year, advance booking is mandatory as unreserved cars fill up instantly. Additionally, popular "special" trains like the Narita Express or certain sightseeing trains are reserved-only, meaning you cannot board without a pre-purchased seat. In 2026, the JR-East and SmartEX apps allow for high-value digital booking up to a month in advance. If you are traveling in a group and want to sit together, or if you have "oversized baggage" (which now requires a specific reserved space), booking at least a few days ahead is the "gold standard" to avoid travel friction.