The typhoon training
Ota is surprised to hear his master's instruction when during their training, a typhoon blows in from sea. Instead of helping his master make preparations in their building, the master sends his student out onto the beach to do battle against nature. He stands there during the whole storm and endures the suffering of blistering winds and rain with tornado and lightning looming ominously nearby. In the end, he is granted his survival by nature, and he has accomplished something through training that Miyagi himself could not have given him.
Pearl Harbor and irony
When the master and student hear about Pearl Harbor, it is ironic for two reasons. It is dramatically ironic because the reader knows what that means for Japan's future. The reader's sense of drama is amplified because they know that life is about to change drastically for these two and for the whole of Japan. The irony is also situationally ironic because Ota and Miyagi expect their mission to be one thing, but instead, they end up defending their cities from foreign invaders.
Ota's call to action
Ota is ironically called to action during the time of his training. Without a chance to feel confident yet about his skill, strategy, or mastery of will, he is called to be the head of defense in Okinawa. This is doubly ironic because his first assignment is basically to panic and struggle to an extreme limit while watching his community be ravaged and murdered by horrifying invaders with weaponry beyond his expectation. This is like the typhoon irony, but instead of enduring nature, he endures human warfare.
Corruption and heroism
The role of the hero is ironically flipped on its head by WWII. Now, instead of protecting or improving the Japanese way of life, Ota has to decide whether it is even appropriate to try and re-establish something from the past way of life. Perhaps WWII and the horrors of the Pacific theater are such that no one will be willing to return to the old way of life. That means that the hero's challenge is to become a civic leader and fight for a new kind of sustainability and peace during a plague of chaos and hopelessness.
