The Odachi pre-dates the Chinese Zhanmandao. Considerably in fact. Japanese great swords inspired the Chinese Zhanmandao. The trouble with the Odachi is that it is not a standard sword. Forms of Odachi have existed in Japan for a long time. (Even before the word Odachi was invented.) Many were offerings for gods, massive swords enshrined in Shinto temples. I've seen some that had blades much bigger than a man.
A nagamaki is also no more than a shorter naginata as well. Although the quality of their construction would vary. Some nagamaki were made from recycled katanas, (This was true for the blades of regular naginata as well.)
Bookmarks