Hi all, I'm new here. I am Kyushudan of the Japanese Castle Explorer website.
First, let me say that I don't know jack about Ukiyo-e. So, all I can really have an opinion in is the castle. And, what castle do I think it is? No idea. Sorry.
I am absolutely certain that whatever castle it was, it did not look as it has been depicted here by the artist. I'm sure Mr Utagawa used the castle buildings that he saw around him as references. For me, the two-story turret has the look of the Sakurada (Tatsumi) Turret of Edo Castle (the Imperial Palace to some.) The three-story turret looks to be similar to one of the remaining turrets of Nagoya Castle. I should clarify that even while I say they look similar, it may just be a coincidence.
Bottom line: the accuracy of the castle is not important to the scene.