Sakiyoken

It is in Tokyo Character Street. You can access from the Yaesu underground center exit ticket gate or Yaesu north entrance ticket gate.

The bento is sold in different ways at the door of the stand.

There was no place to sit much. While waiting for Shinkansen it was hard to hold a big baggage

Usually not. I think that it will be possible if you use a ticket type that allows you to get off on the way, such as a one-day ticket or a tour ticket. Check with your station staff to see if your ticket is available for a stopover.

What is the question? I do not know so please write it concretely.

It is located on the basement floor