This clip explains the mystery of spin sheathing seen in may samurai movies by a step by step approach.
Also check out the flowing if you're interested:
Authentic Samurai website
https://www.authenticsamurai.com
Authentic Samurai Workshop
https://www.airbnb.jp/experiences/224924?s=67&shared_item_type=2&virality_entry_point=2&sharer_id=183648872