A 26-year-old Naho Takamiya and her friends meet outside their old school to dug up a time capsule and read letters they wrote to themselves 10 years earlier, when they were 16 years old and went to the same school. Naho begins her story thinking about the many moments in her past that she regrets, and wishes to tell her 16-year-old self how to change them to avoid future regrets and their consequences...