<Asynchronous hardware systems can be defined broadly as systems whose operation is not synchronized to a global clock signal. Instead, asynchronous systems coordinate system activity using some sort of hand shaking. ....>

IMHO Kato does not fit this definition. Also I think the examiner uses the handshake against us, but it is a perfectly acceptable/required part of an asynchronous clocking system. GLTA

http://research.sun.com/features/async/