Grain of Wheat by Toyohiko Kagawa

The story centers on a young man named Kakichi who lives a difficult life in poverty. His life changes after he converts to Christianity under the guidance of a spiritual leader named Mr. Murano. Kakichi then faces the challenge of living a Christian life in a world dominated by poverty and temptation, while also managing his family obligations, such as caring for his ailing father and dealing with a troublesome brother. 

The novel demonstrates how an individual, through their dedication to reform, can change the environment of an entire village. It emphasizes the importance of a practical expression of Christian ethics.