There are no crowds on the intercity Shinkansen trains so free seats tend to be available. However, it is recommended to book a seat before boarding any train during the following peak seasons: April 27 to May 6. August 11-20.

Whether you must reserve a seat on the Shinkansen (Japanese Bullet Train) depends on the specific train type and your luggage size. In 2026, most Shinkansen lines offer both "Reserved" (Shitei-seki) and "Non-Reserved" (Jiyu-seki) cars; if you have a non-reserved ticket, you can board any train and sit in a designated non-reserved car on a first-come, first-served basis. However, some high-speed models like the Nozomi, Hayabusa, and Komachi are "all-reserved," meaning you cannot board without a specific seat assignment. Furthermore, if you are traveling with oversized baggage (total dimensions between 160cm and 250cm), you are legally required to make a reservation for a "Seat with Oversized Baggage Area" on the Tokaido, Sanyo, and Kyushu lines. Failure to do so will result in a 1,000 yen penalty and the conductor moving your bag. During peak travel seasons like Golden Week, the Cherry Blossom season, or New Year, reservations are essentially mandatory as non-reserved cars become dangerously crowded, and seats can sell out weeks in advance.