During the era when Osaka Castle was built, there were three shoguns. As I had been told by my host family in Japan, they are defined based on an ancient story involving a bird who could sing Japanese songs.
The first shogun was very cruel, and he told the bird: Sing for me or I’ll kill you. So the bird sang his song.
The second shogun, who had built Osaka Castle, told the bird: Sing for me or I’ll make you sing. So the bird sang his song.
The third shogun was very kind, and he told the bird: I’ll wait until you want to sing and then I will hear your song. And after waiting, the bird eventually sang his song.
The second shogun had been poor growing up, and he built Osaka Castle as a symbol of his new-found power and wealth.
Eventually it was taken from him by the kind shogun during a war, making him the new leader of that area.
It is now a museum for people to come and see the history of Osaka, Japan.