Halloween culture in Japan has changed greatly in recent years.
Originally in Japan, Halloween was not popular, thus only some foods and items related to pumpkin were sold a little in the past. But in recent years it has become a festival that people cosplay and walk around the downtown area. These cosplayers says “Trick or Treat” but no one expect for treat, and adults are more enthusiastic than children.
By the way, the original purpose of Halloween is to greet the soul of ancestors. It is called “Obon” in Japan. Generally it is customs around August 15th. Japanese people visit the grave in Obon. Of course without doing cosplay.