Luggage

Hi there,

Taken directly from JR-East:
You may bring up to two pieces of baggage on board free of charge. For each bag the total of the length, width and height must not exceed 250 centimeters, the length must not exceed two meters and the weight must be no more than 30 kilograms.

In general this is not strictly regulated, however know that Shinkansen only have limited space for luggage and although you could probably take a little more aboard than the above, I would not recommend it.