At the beginning of Sonic Unleashed, Marcantonio had just returned home to Spagonia after having been gone for a while, and wondered what the cause of the local uproar in the city was, oblivious to the fact that the Earth had broken into pieces after Dark Gaia’s awakening, but eventually learned about the situation at an unspecified point in time.
When Sonic the Hedgehog and Chip arrived in Spagonia to find Professor Pickle at Spagonia University, Marcantonio met them and explained the state of the city after the planet's shattering to them. Marcantonio then provided Sonic and Chip with directions to the university and remarked that they would recognize it with the busy student surrounding it. When Sonic and Chip later returned to him, Marcantonio heard that Professor Pickle had been kidnapped and took all the latest disasters as bad omens.
As time passed, Marcantonio learned more about the state of the world. When he later met up with Sonic and Chip again, Marcantonio heard how they planned to restore the planet with the Gaia Temples, but Marcantonio did not understand how they planned to do that. The same day, Marcantonio received a letter from a friend in Apotos, who he used to work with, and read that people were going crazy at night in his hometown, a situation Marcantonio had noticed was happening in Spagonia as well. During the following nightfall, Marcantonio met Sonic and Chip again, and told them about the letter he had received and the rumors about the crazy people he had heard, before telling the duo that he believed it was somehow connected to the planet's shattering.
Some time later, when Sonic and Chip passed by him, Marcantonio recommend that they should visit Chun-nan as he had visited it before and had found the culture and scenery there enchanting.
Sometime before Sonic passed through Rooftop Run to get the daytime Gaia Key, Marcantonio saw two ghosts, Su and Wu, head into a tower. Shocked about the sight, Marcantonio could not believe his own eyes, but was too scared to look inside the tower to confirm what he had seen. Later, Marcantonio saw Sonic and Chip come by, and told them what he saw, though he doubted they would believe him. Regardless, Marcantonio asked Sonic if he could go into the tower on his behalf and look for the ghosts. When Sonic agreed to, Marcantonio thanked him greatly. Sonic later returned and confirmed that what Marcantonio saw was ghosts, which caused him to laugh in joy and was happy to know that he was not seeing things after all. He then asked Sonic if the ghosts were still inside the tower, but was disappointed to hear that Sonic had made them run away. Afterwards, Marcantonio started to wonder where they went and told Sonic and Chipthat he would not mind seeing them again.
Following that, Marcantonio could not get Su and Wu off his mind, and resolved to go on journey to track them down. His search eventually took him to Adabat, where Su and Wu were hiding in nearby forest that was infected with Dark Gaia's Minions, which made Marcantonio worried for the ghosts' safety. He therefore wanted to go there to check them for himself, but it was too dangerous. Just one day after arriving in Adabat, however, Marcantonio saw Sonic in Adabat. Glad to see him, Marcantonio explained his reason for being in Adabat, and requested Sonic to save Su and Wu, which Sonic accepted, much to Marcantonio's joy. After Sonic returned from saving the ghosts, Marcantonio told Sonic and Chip that he knew they were in a bind and thanked Sonic for his help, before remarking laughing that it was a good thing he kept a eye on them.
Afterwards, Marcantonio continued to watch Su and Wu, and found them too funny as they got cornered by monsters and then hid behind boxes and doors. Eventually, Su and Wu opened more up to Marcantonio and started to leap out in front of him and appeared in his dreams. Whenever Sonic and Chip came by Marcantonio in Adabat, Marcantonio announced joyfully to the duo of how often he saw Su and Wu, which he took as a sign that they had become quite close.