Harukaze is a UART16550-based high speed RS-232 interface for MSX and openMSX does not emulate it yet.
There are several 16550 emulators available on the net, even GPLed licensed. It should not be hard to include it on openMSX.
DOSemu, for instance, uses this emulator:
MARK REJHON'S 16550 UART EMULATOR
http://dosemu.sourceforge.net/docs/README-tech/1.4/x2302.html
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see: http://www.hat.hi-ho.ne.jp/tujikawa/ese/harukaze.html