Lots of Yakuza
I saw a lot of Yakuza in Kanagawa and near Inoshima.Not that the Yakuza (Japanese mafia) will target foreigners. It just might be a good idea to know that if you see a Japanese person with lots of tattoos there is a good chance that he or she is connected to the Yakuza. Yakuza are unable to get into a number of onsens (Japanese warm spring spas) or join fitness gyms and the like simply because they are Yakuza. Yakuza can be friendly but, some are intimidating. I've had no personal experiences of intimidation (likely because I'm far bigger and physically imposing that the average Japanese male), but I have seen and heard of cases where foreigners have had some bad experiences with Yakuza. Most of those cases involved the foreigner saying something rude or doing something stupid that upset the Yakuza.