Set in late 16th-century Japan, the film follows a tragic romance between Ogin, daughter of the famed tea ceremony master Sen no Rikyu, and Ukon Takayama, a Christian daimyō. From childhood, they share a deep bond, and Ukon first introduces her to the Christian faith when she is sixteen. During a visit to her father's house, Ogin confesses her love for Ukon, but the reality of his marriage creates an obstacle that cannot be overcome. Soon after, Shintaro, a merchant from the powerful Mozuya family, asks for Ogin's hand in marriage. Her mother warns that refusing could bring consequences for her father, and Ukon does not oppose, so Ogin reluctantly accepts.
Two years pass. Ogin's husband Shintaro resents the fact that she still loves Ukon, even as he presses his own advances. The political climate worsens, with anti-Christian policies taking stronger hold, and Ukon, steadfast in his faith, is sent into exile. Ogin and Shintaro share one final meeting with Ukon before he departs, partly because Shintaro hopes to sustain business ties with him. After the farewell, Ogin witnesses a young woman being executed for refusing Hidetsugu's advances as a mistress, a moment that starkly underscores the peril surrounding faith and personal choice; the young woman meets her fate with calm resolve rather than fear.
Later, during a tea ceremony at the residence of daimyō Hideyoshi, Shintaro encounters military commander Mitsunari Ishida. Ishida schemes to block Ukon's rehabilitation and his planned military campaign, and he proposes a setup that would force Ogin and Ukon into a meeting that could be used to prosecute both. The couple is ensnared momentarily, but they manage to slip away before authorities can seize them. While sheltering in a farmer's hut, Ogin learns that Ukon's wife has died, and the two spend the night together in a quiet, fragile moment of companionship. When Ogin returns to Shintaro, she asks for a divorce, seeking a path to freedom.
Hideyoshi, determined to turn her into a mistress, invites Ogin to his palace and presses her to reconsider. She refuses, and he gives her two days to decide, threatening that he will claim her father's life if she does not yield. Back at home, Sen no Rikyu organizes a plan to help Ogin flee to Ukon, even contemplating a final act of self-sacrifice to ensure her escape. Yet the house is soon surrounded by soldiers, and the plan becomes a perilous race against time. In the end, Ogin prepares to take her own life once more, entrusting a maid with a farewell fan bearing a note to Ukon, who has taken refuge in Kaga, leaving the fate of the lovers and their world in a moment of tense, unresolved consequence.
