Searching for Cubase 9 and rewire i came across this: http://blogs.yahoo.co.jp/alipapa_p/63031495.html.
(To download: click on ReWire 64-32 Bridge Version 1.3.0 on this page, alas all info about it is in Japanese)
As I am no expert on rewire, and a little curious: maybe one knows more about the ins and outs and can check if it works? - F