Mario Santis occupies the role of an old member within San Podesta Junior, a prominent youth football team in Genoa, and is recognized for his Genoese heritage. He actively observes the initial contentious interactions between teammates Hikaru Yoshikawa and Julian Ray. During this period, Mario steps in as a mediator, attempting to reconcile the conflicts between Julian and Hikaru.

Following Julian Ray's departure to join the multinational Jupiter Wings, Mario Santis steps into the captaincy of San Podesta Junior. He leads the team during its participation in the Junior Champions Cup. As captain, Mario dedicates himself to mentoring younger players, specifically guiding Renato. He facilitates Renato's development within the San Podesta Junior framework, aiding his transition into the role previously held by Julian Ray.