Kessié signed for Atalanta on a free transfer at the end of August, fending off late interest from Juventus to complete a move that takes him back to the club that gave him his professional debut as a teenager arriving from Ivory Coast.
The 29-year-old spent five years at Milan before spells at Barcelona and, most recently, three years in Saudi Arabia with Al-Ahli.
"Coming back here was a choice made with the heart. I thank the club, and Luca Percassi especially — I've come home," Kessié said at his official presentation. "I was just a kid back then, and today I've become much more mature than I was ten years ago. I'm proud to be here and to be part of this big project."
Reflecting on his time in Saudi Arabia, the midfielder said the experience had left him refreshed rather than diminished.
"As I always say, 'Franck is always ready,' and I can't wait to get started again. It was a great experience outside of Europe — I spent three years there, and it did a lot for my career," he said.
He also spoke warmly of crossing paths with fellow Ivory Coast internationals Amad Diallo and Odilon Kossounou at this summer's World Cup. "I found a piece of Bergamo at the World Cup. I was happy to see them — I've played with Odilon on the national team, and I've known Diallo since we were both very young."
On his role under new head coach Maurizio Sarri, Kessié said he was open to playing anywhere across midfield.
"We work together every day. Playing as a mezzala or even as a deep-lying playmaker isn't a problem for me. The priority is giving everything for the team," he said.
Kessié credited Atalanta with making his career possible in the first place, having arrived in Bergamo from Ivory Coast as an 18-year-old.
"They gave me everything. Atalanta made my dream of becoming a professional footballer come true. I chose Bergamo because it's a choice from the heart," he said, also paying tribute to former teammate Willy Ta-Bi. "We had an exceptional bond, we even shared the same agent. He was a good guy and unfortunately everything changed — he's part of my story too, someone who wasn't lucky. We're here, and I'll play for him as well."
Asked whether he could see himself retiring at Atalanta, Kessié did not rule it out.
"It wouldn't be a bad thing, but for now I'm thinking about the present. We'll see about the future — but why not?"