Blackthorne wakes after thirty-six hours’ sleep to find Toranaga’s galley anchored off Totomi. After eating, he joins Toranaga and the crew swimming. At Toranaga’s insistence he demonstrates diving; several samurai fail before Blackthorne teaches a simpler method. Mariko bravely attempts and succeeds, impressing Blackthorne and building quiet rapport.

That evening, Toranaga, Yabu, Mariko, and Fujiko hear Blackthorne discuss climate, famine, and sea power. Mariko recounts the Mongol invasions and the Divine Wind. Blackthorne outlines England’s naval capacity and proposes supplying and training a modern Japanese fleet via flotillas over years, anticipating resistance from Iberians.

Intrigued but noncommittal, Toranaga questions details, then defers his decision. When Blackthorne requests language aids, Toranaga agrees to help obtain Jesuit grammars so Blackthorne can learn Japanese.

At dawn, Toranaga releases carrier pigeons: orders to Kiritsubo for Hiro-matsu to attempt a peaceful departure from Osaka, but to fire the castle section and commit seppuku if blocked; and to Sudara in Yedo to continue secret war preparations. The galley turns north along Izu.

Near Cape Ito, a cliff collapses during an earthquake, briefly halting the oars. Mariko explains Japan’s frequent quakes, fires, Great Waves, and tai-funs—the ever-present nearness of death. With the danger passed, they resume the voyage toward Anjiro.