Seventeen-year-old Nanaka Kirisato is a high school student serious about her studies and goals in life. She frequently criticizes her best friend, Nenji Nagihara, for being a childish delinquent who spends his time fighting other boys. Then one day, after a heated argument with Nenji, she falls off a flight of stairs and suffers a brain injury, resulting in her mind reverting to that of a six-year-old. With this in mind, Nanaka's father and Nenji must keep her injury a secret as she struggles to live a normal life and grow up all over again.

Alternative title:

• Nanaka Juu-nanabun no Roku (Japanese)
• Nanaka ma quanti anni hai? (Italian)

Nanaka 6/17 DVD (TV): Complete Box Set Episode Titles:

• 1. Nanaka Kirisato, 6 Years Old!
  
• 2. Pianist Nanaka
  
• 3. Big Sister Nanaka
  
• 4. 3 People With a Good Relationship
  
• 5. Nanaka's Triple Date
  
• 6. School Excursion Nanaka
  
• 7. Continuing Trip Nanaka
  
• 8. Nurse Nanaka
  
• 9. Cultural Festival Nanaka
  
• 10. From Nanaka to Nanaka
  
• 11. Domikaru Nanaka
  
• 12. Nanaka Kirisato, Age 17
  
• 13. Nanaka the Distraction (Unaired TV Episode)