Mr. Tsujihara said his ambassadorial style — “behaving like a human being” is how he put it — reflected his unpretentious upbringing in Petaluma, Calif., north of San Francisco. His parents, second-generation Japanese immigrants who were forced into California internment camps during World War II, owned the modest Empire Egg Company there. The youngest of five children, Mr. Tsujihara grew up making egg deliveries. Summer jobs included sorting eggs on a conveyor belt and mucking chicken coops.

After earning an accounting degree from the University of Southern California and an M.B.A. from Stanford, he founded a business called QuickTax that went belly-up. In 1994, through contacts at Ernst & Young, he got a job at Warner managing character licensing for Six Flags theme parks, among other duties. Soon, he was climbing the rungs.

Wherever he learned the skill, his deft touch became clear to Hollywood’s creative community last September. That is when Warner announced that Ms. Rowling had agreed to adapt for the big screen her “Fantastic Beasts and Where to Find Them,” a 2001 book billed as one of Harry Potter’s Hogwarts textbooks. Three megamovies are planned. The main character will be a “magizoologist” named Newt Scamander. The stories, neither prequels or sequels, will start in New York about seven decades before the arrival of Mr. Potter and his pals.

Convincing the famously independent Ms. Rowling to dive back into film was a coup. “When I say he made ‘Fantastic Beasts’ happen, it isn’t P.R.-speak but the literal truth,” Ms. Rowling said in response to emailed questions. “We had one dinner, a follow-up telephone call, and then I got out the rough draft that I’d thought was going to be an interesting bit of memorabilia for my kids and started rewriting!”

She added, “When Kevin got the top job, he brought a new energy, which rubbed off. He’s a very engaging person, thoughtful and funny.”