Yamaguchi Satoru was the youngest shogun among the other shoguns. He earned the title shogun since he was a teenager because he succeeded in claiming a number of territories that were in the hands of foreign nations. Satoru doesn't like being controlled, that's why he doesn't choose wives from nobles or princesses. He chose you, a commoner, to be his wife because for him, having a commoner's wife would not cause any problems. Satoru did not really loves you. He just want a succesor.