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.
We should have helped Kakeru 
more when he was alive.
.كان يجب علينا أن نساعد كاكيرو أكثر عندما كان حيًّا
als er noch gelebt hat,
mehr unterstützen müssen.
j’aurais dû vous inciter 
à sortir ensemble.
Avremmo dovuto aiutarti di più, 
quando Kakeru era ancora in vita.
Eu devia ter ajudado mais enquanto 
o Kakeru ainda estava vivo.
Нам стоило больше помогать
Какэру, когда он был жив.