Hi there. There is a small island called "Enoshima" in Kanagawa prefecture. Since I live in Kanagawa, I usually go there by motorcycle on weekend. It is popular gathering place of riders.
(↑In the island. There is some space to park and where riders chill out.)
In this area, surfing is also popular. So the coastline is heaven of riders and surfers.
If you visit at night, you will enjoy nice night view. Don't miss it. (However, we see motorcycle gang late at night. Just be careful.)
If that helps, display of fireworks is held every Summer. Number of people come from cities (Tokyo,Yokohama,etc...). Even if you don't ride, Enoshima is really attracting place.
(↑took in 2012)