Near Shibuya Station in Tokyo lies the Shibuya Scramble Crossing.
It is said to be the busiest pedestrian crossing intersection in the world, where upwards of 1,000 people cross during each traffic light cycle. It's a beautiful sight, especially at night with all of the towering buildings lit up:
There's lots to do in Shibuya, including what is likely the world's largest remaining CD record store, Tower Records, with a massive eight floors filled with music CDs from every genre you could imagine: both Japanese and imports.
However, it is not for the feint of heart, for folks afraid of crowds. To get there and back typically requires going through Shibuya's train station, where more than 2.4 million people pass through each and every day.
Your bet bet is to avoid rush hour, which in Japan means around 7am-10am, and then 5pm-11pm. Yeah it's a bit longer than an hour. But go during those times and the trains are likely to be filled far beyond maximum capacity. I've yet to see any actual train pushers here, but I've heard it's very much a thing that sometimes happens. However, I have seen firsthand that when a train is completely filled, sometimes people will dash toward the full train cart, spin around backwards, and push themselves inside, grabbing onto the railing to ensure they are not immediately ejected back out. It's not fun being a passenger inside the train during this experience, which I can say from firsthand experience.
Still, if you can bear the crowds, it's definitely one of the highlights of a trip to Tokyo. And again, I highly recommend seeing it at night as well! The architecture alone is well worth the trip.