Halloween finished at the end of October and you can see many Christmas ornaments, trees, and illuminations everywhere in the cities in Japan too.

Over the past few years, the number of Japanese who enjoy Halloween has increased rapidly, especially among the young generation. One of the reasons is because of businesses after all.
After the hot summer, which has a lot of events like fireworks and festivals, has passed and when the Christmas season starts, Japanese are putting more importance on Halloween in the same way as Western countries. 

Different from Christmas day, probably most Japanese don't know why people celebrate Halloween.
For Japanese, Halloween is a special day when you can disguise yourself with a costume, hold a party with friends or families, and say, "trick or treat" even if you don't know the meaning. 
Why Japanese people like Halloween and Christmas same as Western countries?

As for Christmas, some people have asked me before, "why do you Japanese celebrate Christmas even though you aren't Christian?" the answer was simple, "It's not religious event but a festival for Japanese." Whatever we enjoy, we are all fine after all. 

But it hasn't been long since we start celebrating Halloween. We can say it's still just an imitation of Western countries. 
I believe Japanese are good at imitating something first then developing it into a Japanese style. We call it "ガラパゴス化（か) Galapagosization" after the Galapagos islands in which many species have been evolved in an original way. 

Famous Japanese neuroscientist, Kenichi Mogi, said on twitter several days ago that Japanese people evolved Christmas in an original way same as St. Valentine's day. Different form Western nations, Christmas is a couple's event and not only for families and friends in Japan.
Christmas Eve is one of the busiest days for restaurants, shops and hotels(including "Love hotels") throughout the year. We can't think of closing restaurants on Christmas Eve! 

And Dr. Mogi also predicts that even if Japanese Halloween is now just the imitation of Western Halloween, Japanese will evolve it in their own way.
In the near future, you may be able to see a wonderfully Japanese customized Halloween like the Japanese Christmas.