Key of Life is a 2012 Japanese movie written and directed by Kenji Uchida.
A struggling actor named Sakurai considers suicide after a series of career failures. However, before he goes through with it, he stops off at a public bath house where a seemingly rich man named Kondo slips and suffers amnesia after hitting his head.
Sakurai quickly decides to swipe Kondo’s locker key and switches identities with him. However, his newly-acquired life seems to bring him nothing but trouble and danger as it turns out Kondo was actually a professional hitman. Meanwhile, Kondo meets a young woman named Kanae at the hospital and begins settling into his new life.