In 19th century Japan, revivalism to old days came up, and the isolation period started to ending by European and American big war ships. Such a situation rose the demand of swords made by old masters. Then, dealers supplied many fake signature swords. It is called "Kuwana" blades. The reason why such swords are called "Kuwana" is not certain. Some people says it relates with Kuwana clan, other says it comes from the slang "don't be tricked". Anyway some of them are very well made. Even today, they are treated as genuine sometimes.
Probably there were many smiths who accepted the order to make fake swords. They were weak, and had to win bread for their family. One of the most famous counterfeiters is Gassan Sadaichi who became the first Living National Treasure later. Another famous smith is Naomitsu who put fake signatures on other blades.
The left is a Kuwana blade, the right is genuine from a book.
Kuwana blade of Takamitsu
