Right, I had forgotten that Bismarck engaged Musashi in a battle. For some reason I thought she was either undamaged or repaired somehow. Now that's even more of a suicidal move to challenge Gunzou's forces to a battle for a certain someone's sightseeing. I don't even remember much about that suspiciously long-lived group of four (maybe three, as Kaoru doesn't seem to be alive anymore) that includes Gretel, but I'll assume Kaoru is an ancestor of Gunzou, and that is why Berlinetta wanted to see him.