New rule for bringing big baggage.
New rule for bringing large baggage into Shinkansen trains will be applied from May 2020. If a passenger bringing a baggage of the total linear dimensions (length, width, height) per item is from 160 cm to 250 cm, they must pre-order a ticket. A passenger having no advanced reservation for his/her baggage will be collected a fee of JPY 1,000.
For details, refer the article in Japanese.