Ken Watanabe in Memories of Tomorrow © Yoshikazu Kato/ROAR

Most actors would leap at the opportunity to direct their own film. Not Ken Ken Watanabe.

"A producer asked me, 'Do you want to direct?'" laughs Watanabe about being asked to helm his latest film, Memories of Tomorrow. "I told him definitely no."

If his onscreen persona is any indication, Watanabe would seem like a natural auteur. The 47-year-old actor projects the kind of organic stoicism that could lead soldiers into battle, which he did on screen in last year's Letters from Iwo Jima. But off-screen, Watanabe has performed practically every role but direct on Memories of Tomorrow, in which he plays Masayuki Saeki, a model Japanese ad agency manager who starts to succumb to Alzheimer's disease at an early age. It is a performance that required his full attention as an actor, showing a vulnerable side that the usually robust Watanabe rarely displays in front of the camera.

Although Watanabe had his own health scare in 1989 when he was diagnosed with acute myelogenous leukemia (from which he has recovered fully), the actor says the story of Saeki, who is forced into retirement and is cared for by his wife, actually reminded him of his parents.

Ken Watanabe in Memories of Tomorrow © Yoshikazu Kato/ROAR

"My father had a stroke when he was 43 years old, and half of his body was paralyzed, and my mother has cared over 30 years for him," says Watanabe, with the help of a translator. "I didn't realize before shooting and in the middle of the shooting, I discovered how close the situation between my parents and this couple. At the end of filming, I wanted to dedicate this movie to my parents."

That is only one of the many creative fingerprints Watanabe has left on Memories, his first film as a producer. Watanabe bought the film rights to Memories after he read Hiroshi Ogiwara's novel on the set of Memoirs of a Geisha in 2005. Says Watanabe, "After I read the book, a warm feeling remained in my heart, and as an actor and filmmaker, we wanted to convey to audiences the same feeling."

Audiences in Watanabe's native Japan responded enthusiastically to Memories, which earned the actor numerous best actor prizes, including the Japanese Academy Award. Yet Watanabe has remained committed to those suffering from Alzheimer's disease long after Memories stopped production. When he won an award for his work as a producer on the film, Watanabe donated the accompanying cash prize to Japan's Alzheimer's Association. But before all the accolades, Watanabe may have received his biggest vote of confidence and saw the impending impact of Memories when he screened the film for Alzheimer's patients and their families.

"That was a really high hurdle," says Watanabe, who wanted to make sure his depiction of the disease was accurate. "[After the screening], a really warm feeling remained in the theater and [one patient's] wife said that her husband has Alzheimer's, but she couldn't understand his feelings when he got fired from his company. And after seeing this movie, she completely understands his feelings."