In the several years I have been here the presence of Halloween has increased a lot. My own guess is that a lot of it is due to Tokyo Disneyland marketing Halloween events at the park which have turned out to be pretty popular. Seeing the Disneyland success (my guess) might be the cause of other shops and businesses jumping on the Halloween bandwagon and selling candy, baked goods etc with Halloween touches. Some shops also may use simple Halloween decorations inside or out to attract customers.
At English schools, especially children’s classes, there may be a party where the children dress up, play games and have candy. At some kindergartens and preschools the parents may come dressed up too and the few times I have seen this there is always one woman dressed as a nun. I have no idea why the nun costume is seemingly so common and am amazed that there is even one sold here at all. Some English schools have a Halloween party for the adult students after class at the school while many foreign teachers seem to prefer to dress up and go to a club or go to a fellow teachers apartment and drink.
As far as I know the average family does not do anything at home for Halloween. No trick or treating, no pumpkin carving or any other type of activity, or special food.
Most people aren’t aware of the rather diverse history of Halloween let alone that the name is short for all hallows eve or even and the day after is a Catholic feast day from which the name derives.
A quick aside to say that when I write that most people here, meaning most Japanese aren’t aware of such and such a thing I do not mean that statement in a negative way it is simply coming from my observation and experience that people simply have never heard certain information.