Mai, who has a quiet and gentle personality, lives with her father. Mai is an honor student and is a good only child who does both her studies and housework. But Mai has a secret daily routine. Every morning, she takes care of his morning erection with her mouth, and before going to bed, she opens her pussy and makes her father spit his accumulated sperm into her vagina... A forbidden act that cannot be told to anyone. A record of incest that has become part of everyday life.