"At the same time, I didn't want to be just a bad guy. I wanted to put humanity in this role. [Matsuhiro] was both crazy and sadistic, but also weak and traumatised."
Miyavi, real name Takamasa Ishihara, added that Jolie wanted to "make a bridge between all countries that had conflict".
"She was very persuasive," he said. "It's a story that is still painful for my country and after filming some of the more violence scenes, I couldn't stop crying."
Jolie became close with Zamperini shortly before his death aged 97 last July, and was sure to show him an early cut of Unbroken.
Watch the trailer for Unbroken:
App users: Tap here to view video
"I was more emotional than he was," she said. "I went in to take care of him and he was taking care of me. It was an extremely moving experience, to watch someone watching their own life."
Jolie is currently directing her husband Brad Pitt on romantic drama By The Sea, about a married couple going through some difficulties.