AecStreamAcGi::drawText() is not properly drawing Japanese characters. You can reproduce this, using Graffiti OMF SDK sample. Change the text style (command "style") to MS Mincho, and draw some text. English characters show fine, but Japanese characters show as "???". This was working with 2012 and earlier releases.
In AutoCAD Architecture (ACA) 2013, a feature called Progressive Update was introduced. Unfortunately, the change to support this feature has affected AecStreamAcGi::drawText() API, and it is working properly. A workaround till the issue is corrected in the product is to turn off the progressive update feature; use the command "setEnableProgressiveUpdate" >> "No".