Based on the Japan Railway Company (JR)’s website on luggage information, we highly recommend that you bring a suitcase that will not require reservation on the trains. Do measure your suitcases to make sure that the breadth, length and width do not add up to more than 160 centimeters or 63 inches. This would usually equal a medium size luggage, like the one Dr Bonk showed you on Saturday. Here is the link to the JR website. https://global.jr-central.co.jp/en/info/oversized-baggage/