Why could Kawasaki generate Z1/Z2, the unparalleled masterpiece motorcycles, nearly 50 years ago?

When bikers define the motorcycle, it is Kawasaki’s Z1 or Z2. Do you know the contexts in which such masterpieces were born? This story gives the histories of how Kawasaki gained the fame around the world by these two bikes in 1970’s and the fascinations of them.