Mastery and learning
The original imagery of the book is the imagery of ancient martial arts from Asia. The master in this novel is a real historical character, a founder of an important school of Japanese martial arts which is called Goju-Ryo and is a type of karate. The master is shown in tandem with a student who deeply reveres the master with almost religious sincerity. The portrait of the novel takes them forward in time until the death of the master, showing how the student is assisted in attain his own mastery by the selfless sacrifice constituted by the master's teaching.
Onslaught and survival
The book features survival as a major form of imagery. For Ota, enduring a difficult training has the feel of surviving an onslaught, and indeed, when his master sees a typhoon coming, he hands the training reins back to nature. The master tells the student to endure the typhoon standing on the beach, a kind of battle against nature. Later, Ota endures a similar onslaught when his city is invaded in the Battle for Okinawa. He survives that in a leadership position, which means that he has a fairly comprehensive understanding of the battle in real time.
WWII and history
The horrors of WWII enter the novel the same way the reader might have expected it to historically occur. Although sometimes people have warped perceptions about geopolitical warfare, it isn't like the whole of Japan got together and plotted Pearl Harbor. That was an unwelcome surprise for these karate teachers. This means that war is probably going to come to their homes, and they ready themselves to do combat. The war imagery is striking, because the hand-to-hand combat of karate is almost irrelevant given the machinery of modern warfare.
Rebuilding from chaos
The whole novel has an imagery running through it of balance and order. That is a major distinction in their philosophy as martial artists. Their lives are specifically oriented around balance. They are training their minds too, not just their bodies, readying themselves on all fronts to an inevitable call to action. The goal of their martial artistry is to become absolutely effective if they are compelled by circumstance to intervene in a given situation. This takes them from peaceful days to days of horror and warfare, and the novel ends on a final chord of chaos, implying a future of rebuilding and restoring.
