Tokyo does not become less busy during Golden Week (for tourists)
Want to firstly preface this that this is from the perspective of a tourist. I can see local neighbourhoods quiet down for those living here but most tourists will be hitting up points of interest.
Was in Tokyo for the past few weeks so sharing my experience of Golden Week. Heading into this trip I looked into how Golden Week would be in Tokyo and there was a lot of comments here saying Tokyo actually becomes less busier than usual. But from my actual experience I did not find this true at all - at least from a tourist perspective.
I arrived in Tokyo before Golden Week started and those days will be my frame of reference. The week days of April 22-24 were pretty quiet. Went to places like Shibuya, Shinjuku, Akihabara and while there were still lots of people as expected of a large city, it was very manageable and few lines until the evening when people got off school and work. Then came the weekend and suddenly everything was a lot busier as to be expected. You also saw people lining up for things in the morning for places that didn't have lines on the weekdays.
The following week had Wed, April 29th as the only actual holiday but some sites said this could be considered part of Golden Week. Monday and Tuesday were pretty much regular weekdays. Then came Wednesday, the holiday day. This day was pretty much the same as the previous weekend days and noticeably more busy. Thursday and Friday were then back to regular weekday crowds. I was told it was common for locals to take the in-between days as vacation days to chain the holidays but I don't think it made that big of a difference for Tokyo. Maybe the people who do chain the holidays were more likely to travel elsewhere for a long trip.
Now came the bulk of Golden Week, Sat May 2nd through Wed, May 6th. These five days were crazy busy. A noticeable increase of people in Shibuya, Shinjuku, and Ikebukuro compared to even the weekend crowds. Harajuku's Takeshita street and Skytree were packed as were malls like Sunshine City or Parco. For lunch, a lot of places in major city centres like Shibuya and Shinjuku that didn't have a wait during regular non-GW weekdays now had 30 min+ waits. On one evening, went to an Izakaya in Shinjuku with a buddy and it was an 1.5 hour wait. On other nights, I went to restaurants in quieter areas and those didn't have a wait. The only thing you could say was less busy was the lack of a regular train rush hours. On regular days I tried to avoid the rush hour periods as the trains were actually packed but the trains were way more manageable during those hours during these days.
Once Thursday came, things returned back to how it was like during a regular weekday. I assumed people would take those days off to chain the holiday days but I guess like I mentioned before, the people who chain the holidays might be traveling elsewhere.
Hope this provides a frame of reference for those planning trips during Golden Week.