The letter from the future details the regret felt by everyone for being unable to celebrate Kakeru's birthday. As such, high school Naho and the gang pester Kakeru about what he wants until the big day. On the other hand, 26 year-old Naho and the gang gather at the late Kakeru's grandmother's house to celebrate his birthday, like they had promised in the past.
There's only one regret:
:لديّ ندم واحد
Ich bereue nur eine
einzige Sache.
Nuestro único arrepentimiento
Nuestro único arrepentimiento
Nous n’avons qu’un seul regret.
"Il mio rimpianto più grande è questo:
Nós temos apenas um 
grande arrependimento:
Я сожалею лишь о том,