Things you'll miss):
Space, green, flowers, space again, and some more space.
Pretty photos on calendars and promotional posters with all the beauty of Sakura trees and mountains is another world. What most don't know is the size of crowds gathering in/around those. For every tree in the city there must be thousands of people craving some green. It's a scary view except for the west side that is closer to the mountains and still has landscape untouched (at least for now) by the unyielding and ruthless construction industry who's only purpose is to find and seize any remaining patch of land with the sole purpose of erecting another modern architectural atrocity that will hover over your head covering the sun protruding its limbs to the sky.
That explains the sad figure of only 3.2% green space in Tokyo area with most of it being on the west side. For the comparison, London has over 40%.