Kokoro (Japanese for "heart") tells the story of a subtle, moving friendship between two nameless characters, a young man and an enigmatic old man referred to as Sensei. Tortured by tragic secrets that have cast an enormous shadow on his life, Sensei slowly opens himself up to his young disciple, confessing indiscretions from his days as a student that have left a trail of guilt and that reveal—in the seemingly insurmountable abyss of his moral anguish and his fight to understand the mysteries of love and fate—the profound cultural change from one generation to the next that characterized Japan at the beginning of the 20th century.