Kaze no Na wa Amnesia Movie

A Wind Named Amnesia, 風の名はアムネジア , Kaze no Namae wa Amunejia, The Name of the Wind is Amnesia

It happened quite suddenly, with no warning - all the memories of all the people on Earth, swept away as if by a sudden wind. In a post-catastrophic Earth populated mostly by savages without memories of their past civilisation, one man travels on a journey of enlightenment and hope, across a devastated America.