Halloween caught on in Japan in the last two decades. Despite the costumes, treats, and decoration, Japanese people don’t know the origin or traditions of the festival.
here are some resources in Japanese to share with friends and family. https://www.city-cost.com/blogs/TonetoEdo/wka3L-living
A lot of people say it's 収穫祭 harvest festival but I don't have the same understanding on Halloween. I wonder where they got this knowledge ^^