The area used to be a hill with a monument to the emperor and some dodgy izakayas and snackbars, the leftovers of a postwar black market.
It was all razed in 1994 to build the Southeast Exit Plaza we're all familiar with now.
More photos from google images: https://www.google.com/search?q=%E5%BE%A1%E5%A4%A7%E5%85%B8%E5%BA%83%E5%A0%B4&udm=2
Source: https://www.threads.com/@tokyo_timeslip
There's also a cool book with all the pictures.
by biwook