Suitcase in Tokyo while we travel

I am wondering if it is possible to leave a normal sized suitcase in Tokyo for 13 days while we travel. We will return to Tokyo and then fly home but I understand large suitcases cannot be taken on the shinkansen. Also has anyone heard of the Shinkansen Rail Go Service that operates in Tokyo station? I've heard they hold suitcases upto 15 days but just need more info!!
Thanks in advance.

Rail Go Service Office is near the Yaesu-Minami (=south) exit of Tokyo station.
410 yen/day for the first 5 days and 820 yen for 6-15 days.

I didn't have much trouble taking full-size luggage on shinkansen trains - it's mostly a problem on smaller lines (e.g., in Kyushu) and on trains running during rush hours (7-9 in the mornings and 5-8 in the evenings). Other than that, we never had a problem finding space on the train for luggage.

We arranged with the hotel we stayed in Tokyo and they agreed to store our baggages with them free of charge while we were exploring other places. But that was for a short period of 4 days not two weeks though. Try the hotel you will be staying and they might oblige you. Good luck!

Will the Rail Go take large suitcases for eg, normal luggage size?

Do you think the hotel I will be checking into will hold the luggage from the 19-30 Dec? I am staying in a different hotel before I travel! Thanks again in advance