In the late Edo period in Osaka, a young girl named Shunkin is born as the second daughter of the wealthy Mozuya merchant family. Blessed with a natural genius for dance and striking beauty, her life takes a tragic turn when she loses her sight to an illness at the age of nine. Forced to abandon dancing, she dedicates herself to the path of music, becoming a prodigy on the shamisen and koto. Her blindness, however, shapes her into a person of fierce pride, a perfectionist with a cruel and sadistic temperament that inspires both awe and fear in those around her.

Attending to Shunkin's daily needs is Sasuke, a quiet and humble apprentice working in the Mozuya household. He becomes utterly devoted to her beauty and talent, developing an obsession that transcends simple admiration. After secretly teaching himself the shamisen by imitating her lessons, Sasuke is discovered and formally becomes her disciple. This marks the beginning of what he describes as a sweet hell. Shunkin treats Sasuke with brutal severity, subjecting him to violent physical punishment for the smallest mistakes during grueling practice sessions that stretch late into the night. Despite the abuse, Sasuke endures without complaint, finding a perverse pleasure in his complete subjugation to her will.

Their bizarre master-servant and teacher-student relationship deepens and becomes increasingly exclusive. When Shunkin becomes pregnant, both she and Sasuke deny that he is the father, refusing a proposal from her father to marry. She gives birth to a child who strongly resembles Sasuke but sends it away to be raised by another family. As a young adult, Shunkin becomes an independent shamisen instructor, moving to a new home with Sasuke still by her side. Her beauty and skill attract many students and admirers, though her violent teaching methods drive most away. Their fragile, codependent world is threatened by the arrival of Ritaro, a wealthy suitor who becomes her student solely to get close to her.