The Madding Crowds
Visit Japan, but expect big crowds during Golden Week
Now that the sakura blossoms are nearing their end, at least in Tokyo, the next 'season' coming up in Japan is Golden Week. (If you still want to see sakura head north and it's possible to have another couple of weeks or more of sakura blossom viewing.)
Golden week this year starts from Tuesday, April 29 (Showa Day) and "officially" ends on May 5 (Children's Day). May 3rd (Constitution Day) and May 4th (Greenery Day) fall on a weekend this year.
Many people will start their vacations from May 26 or 27 and come back to Japan on May 4, but some postpone to take advantage of the first week of May.
May 3rd is predicted to be the heaviest travel day for people leaving Japan and May 5th and 6th will be very crowded with people returning. Airports, train stations, and highways will be jam packed. Many hotels and resorts (onsen) raise their prices considerably during Golden Week to take advantage of the heavy crush of vacationers. Overseas destinations like Hawaii, mainland USA, and Southeast Asia are also popular spots. Airplane tickets are normally at their most expensive during this time too.
On the plus side, Tokyo is a bit calmer during Golden Week and trains and subways are not as crowded as most commuters have the time off. But, expect stores and restaurants to be very busy, especially if the weather is nice.
So, if Golden Week is your only free time then by all means, come to Japan, but just be prepared for the crowds.