Wonderful Fool by Shūsaku Endō

Set in post-war Japan, this novel follows the journey of Gaston Bonaparte, a seemingly naive and clumsy Frenchman, who arrives in Tokyo to visit his pen pal, Takamori. Despite his awkward demeanor and lack of worldly sophistication, Gaston's genuine kindness and unyielding faith in humanity gradually influence those around him, including Takamori and his sister Tomoe. As Gaston navigates through various encounters with the city's inhabitants, his simple yet profound wisdom challenges the cynicism and moral complexities of modern society, ultimately revealing the transformative power of compassion and humility.