You can bring large luggage on Japan Railway (JR) trains, but in 2026, there are strict advance reservation rules for "Oversized Baggage" on high-speed Shinkansen lines (specifically the Tokaido, Sanyo, and Kyushu lines). Any suitcase with total dimensions (length + width + height) between 160 cm and 250 cm requires you to book a "Seat with an Oversized Baggage Area" or "Oversized Baggage Compartment." This reservation is free if made at the time of ticket purchase, but if you board without one, you will be charged a 1,000 yen penalty fee and may be required to move to a different car. Baggage exceeding 250 cm is not permitted on the train at all. For standard "carry-on" sized luggage (under 160 cm), you can use the overhead racks as usual. To avoid the hassle of navigating crowded stations with "big luggage," many travelers in 2026 utilize the Takkyubin luggage forwarding service, which delivers bags from your hotel to your next destination for a small fee, allowing you to travel on the Shinkansen with just a small day bag.