Documentaries typically do not feature actors or actresses in the traditional sense. Instead, they feature real people, such as the subject of the documentary, experts on the subject, and archival footage.
Therefore, it is likely that the film features Alekos Fasianos himself as the central figure, alongside art critics, historians, and other individuals who have insights into his work.
If you'd like to learn more about who is featured in the documentary, I recommend searching online for information about the film's production or reviewing the credits.