For Diego Luna, exploring the backstory of his Rogue One: A Star Wars Story‘s character in the new Disney+ series Andor was an “immediate yes.”

Six years after Cassian Andor was first introduced in Rogue One, the series, which dropped its first three episodes Wednesday, sees Luna back to fill in the blanks about who his character is at his core.

Luna, 42, told Good Morning America the Star Wars universe is unique in that “there is a chance to answer every question — and there was no answer to who this guy was.”

“To me, Rogue One is a film about an event,” he said. “You get very little hints of who the characters are.”

In that film, Cassian joins with a band of rebels, led by Felicity Jones‘ Jyn Erso, to steal the Galactic Empire’s Death Star plans. The events lead directly into 1977’s Star Wars: A New Hope. While the crew is ultimately successful, they all perish in the mission — including Cassian.

Luna called it “fascinating” having the chance to go back and explore what needs to happen in someone’s life for them to make “that ultimate sacrifice.”

In Andor, “it’s about the nuances. It’s about the little details, the different layers,” he explains.

In Rogue One, Cassian states that he’s been “in this fight since I was 6 years old.” According to Luna, the new series asks, “What needs to happen in the life of someone to believe he’s capable of something like this, to connect with a cause in this way?”

While Andor mostly focuses on Cassian, it also sees a few returning players from Rogue One — like Genevieve O’Reilly‘s Mon Mothma and Forest Whitaker‘s Saw Gerrera, as well as a cast of newcomers, including Stellan Skarsgård, Adria Arjona, Denise Gough and Kyle Soller.

Disney is the parent company of Lucasfilm as well as ABC News.