[Radu Transylvanicus]

Between 1543 until 1650 In Japan took place what was called the "Nanban Period" where foreigners were allowed to enter the the country, most of them merchant visitors from China, Holland, Spain, Portugal and England... That until the feudalist politics initiated the ,,Seclusion Laws" that forbided almost any foreigner to enter Japan and the country become completely isolated for centuries... (The Wikipedia Encyclopedia)
The same Wikipedia Encyclopedia article continues : "One thing the Japanese were definitely interested in was barbarian guns. The first three Europeans to reach Japan were Portuguese and came on a Chinese ship to the southern island of Tanegashima, and they had arquebuses and ammunitions with them. At that time, Japan was right in the middle of a huge civil war called the Sengoku period (Period of the country at war). Strictly speaking, the Japanese were already familiar with gunpowder (invented by, and transmitted from China), and had been using basic Chinese guns and cannon tubes called Teppō (鉄砲 Lit.”Iron cannon”) for around 270 years before the arrival of the Portuguese. The Portuguese guns however were light, had a matchlock firing mechanism and were easy to aim with."
I realise of course the enormity of distances and how historicaly separated European Transylvania and insular Japan are but here is a theory for the start we can evolve by reading the above !
All that in case it was inspired by Japanese and not a Chinese sword !