Are you referring to a German UBoat turned over to the Japanese? A couple of routes. First, probably the easiest way, is you could alter the DefSide.cfg file (in the Roster folder) for the Germans, to not surrender and become 'neutral' in May. Make it August. Second, probably the correct way would be to "clone" the German Type IX, either the playable one (if that's what you're after), or the AI one, and make the clones Japanese.
