Why does Cio-Cio-San remain certain that Pinkerton will return?

Cio-Cio-San’s unwavering certainty that Pinkerton will return is rooted in her deep devotion and her interpretation of their final morning together. Before he departed, Pinkerton promised her that he would return when the robins make their nests.1

Despite the passage of three years and the skepticism of others, she clings to this promise as a vow of fidelity. Her conviction is famously expressed in the aria "Un bel dì," where she envisions the day his ship will appear in the harbor, vindicating her love. Furthermore, she rejects all other marriage proposals—including those from the wealthy Prince Yamadori—because she maintains that she is already married under the laws of the United States, which she believes will protect her union. Her faith is so absolute that she even keeps their child, whom she intends to rename "Joy" upon his father's return, as a testament to their bond.1