As can be seen pictures, these cars are built in big speakers on rear side.
These speaker is basically not for enjoying music while driving. They enjoy music at parking with incredible big and unbelievable high quality sound.
Even though there are no specific base car, lots of Sotomuki car is basically Van type or Wagon. and some people dress up whole car, some people spend money only for making their sound system more crazy one.
Their sound from speaker is really big, so they need suitable place to enjoy their sound system. Japan is very narrow country, and Japanese people is very nervous. If sotomuki car make a good sound, people never enjoy with them. they just call to police, and ask to kick out such funky guys. They never enjoy music, but they enjoy watching police working. What’s a poor Japanese !
so this parking, Daikoku PA is holy place for these sotomuki guys because this is isolated PA where there are no residential place around there. Every week end, sotomuki people come to daikoku PA to enjoy there lovely sound system.