Ness is the eldest son of an unnamed couple, and the older brother of Tracy. One fateful night, Ness awoke from a sound sleep by the terrifyingly loud impact of a meteorite north of his house in Onett. His mother and sister are agitated, but Ness left to find out what happened. After meeting up with Lier X. Agerate and his next-door neighbor, Porky Minch, Ness returned home and tried to fall back to sleep only to be awoken several hours later. Porky had arrived and demanded (Ness read as ‘asked’, Porky never was good with expressing himself.) that Ness help him look for his little brother Picky, who had gone missing during the calamity surrounding the impact.

After a pep-talk from his mother, Ness, Pokey, and King go back out to the hillside, and find Picky (who reveals it was Porky who actually ran away). They also encountered Buzz-Buzz, an insectoid warrior who has returned from the future to warn Ness of the threat that Giygas poses to the universe. It is from Buzz-Buzz that Ness learns of the prophecy surrounding his future; that he, along with the help of two other boys and one girl, will stand against Giygas and save the universe from total annihilation.

Vested with this knowledge, Ness accompanies Porky and Picky back to their home but is assaulted by a Starman Jr. The alien confirms the prophecy before attacking the group. It is defeated through Buzz-buzz's massive PSI powers and Ness' physical attacks. Upon arriving at Pokey's house, Buzz-buzz is unceremoniously killed (for his alleged resemblance to a dung beetle) by Porky’s Mom. Before passing on, Buzz-buzz passes on the Sound Stone to Ness and starts him on his quest to save the world.

In the town of Onett, Ness first unlocks the power of Giant Step after tangling with Frank Fly and the Sharks. However, Captain Strong and the Onett Police Force are not happy with Ness investigating private property and ambush him at the police station. They back off and give him the way to Twoson after he beats them in a 5-on-1 fight.

In Twoson, Ness is telepathically contacted by Paula, another member of his party, who asks him to come and rescue her. Learning her whereabouts from Everdred, a friendly gangster, Ness finds his way through Peaceful Rest Valley to Happy Happy Village, which is under the spell of the Happy Happyist Cult. He finds Paula locked in a cell in a hidden house, who tells Ness she had been kidnapped by Porky and gives him the Franklin Badge so that he can withstand the lightning attacks of Mr. Carpainter, the Happy Happyist leader, in order to acquire the key to her cell. Ness confronts Carpainter and defeats him, thereby breaking the spell of Happy Happyism over the valley. Though he blames the situation on the Mani-Mani statue, Carpainter thanks Ness and gives him the key to Paula's cell. As Ness left the building, he encountered Porky outside the door, who apologized for acting so rudely. Shocked, Ness wasn’t able to answer, giving time for the other boy to completely lose any hope of being friends with the psychic ever again. As Porky runs away, Ness frees Paula and the two eventually gain the power of Lilliput Steps from the nearby cave.

They then find the way to Threed after assisting the Runaway Five, a famous jazz band, in escaping a debt at the Twoson theater. The Runaway Five take them there in their van and drop them off. Ness and Paula quickly discovered that the town was under an awful curse and zombies were running rampant. They tried to fight the zombies but are lured into a trap and locked in an underground cell. Paula contacts Jeff telepathically in that moment, and helps Ness overcome the homesickness he was starting to feel while they waited for Jeff. Once the third party member arrived, The three of them conspire with the townsfolk to trap the zombies in the circus tent with flypaper. They then found a secret exit in the back of the graveyard and venture forth to find the source of the zombie scourge.

Following the cave, they come upon Saturn Valley, which is under the threat of Master Belch, who not only had dominion of the zombies but had kidnapped many of the valley’s population. They infiltrated a secret base behind a waterfall near the valley and encountered Belch. Playing on his obsession with fly honey, they easily defeated him and freed the Saturn Valley inhabitants, gaining the power of Milky Well in the process.

Their mission in Saturn Valley completed, they go back to Threed, which is now back to normal, and take the bus to Fourside. Unfortunately, they run into bad traffic in the desert and are forced to abandon the bus and conclude the journey on foot. Arriving in Fourside, they find the Runaway Five has fallen into debt with the city theater yet again. Ness and the gang assist in digging for treasure in a mine in the desert and repay the theater proprietor on behalf of the band.

Later on, while shopping in the Fourside Department Store, there is a sudden power failure and Paula is snatched away in the dark. Hearing a call on the intercom, A raging Ness and worried Jeff go to an office on the top floor where they fight and defeat the Department Store Spook. Looking for clues to Paula's disappearance at Jackie's Cafe, Ness and Jeff unexpectedly stumble upon a fantastical alternate dimension called Moonside. Navigating the oppositely-oriented domain, they discover the Mani Mani statue to be the cause and destroy it, to find that they have been in the storeroom to Jackie's Cafe all along.

At the advice of the Apple Kid, they visit a mysterious man who lives among monkeys in the desert named Talah Rama. He gives them a vital trout yogurt machine. Ness and Jeff use the yogurt dispenser to bribe a maid to let them into the Monotoli Building in Fourside, where Paula is apparently being held. With some unexpected help from the Runaway Five, Ness and Jeff make it to Mayor Monotoli's room where they rescue Paula. Monotli apologizes to them for kidnapping Paula but offers them use of his helicopter to travel to Summers. Unfortunately, Porky, who has been working as a consultant for Monotoli and orchestrated Paula's kidnapping, steals the helicopter and flies away, taunting and sneering at Ness as the latter realizes that their old friend was falling to Giygas’ influence.

The Runaway Five take them back to Threed where they repair Jeff's flying machine and fly to Winters, leaving Eagleland to rendezvous with his father. While Dr. Andonuts remodels the Sky Runner, they find their way to Rainy Circle with the help of the dungeon architect, Brick Road. Afterward, they fly to Summers in the Sky Runner, crashing upon landing.

While in Summers, they visit Club Stoic and Ness chats with a woman who shows him some ‘magic’ cake. After taking a bite, he falls into a slumber and sees a vision of a foreigner from Dalaam named Poo, the fourth and final member of his party. After passing the final test in his training, Ness regains consciousness and Poo teleports to the group.

Poo suggests they visit the Summers Cultural Museum, where they find a hidden exhibit that gives an odd clue about the Sphinx in Scaraba. As they are leaving they get a call from Mr. Spoon at the Fourside Dinosaur Museum meant for the museum proprietor. At the Dinosaur Museum, they find a pothole in the back, leading through the sewers of Fourside to Magnet Hill, in the middle of the city. Here Ness picks up a Carrot Key, which he uses to find Pink Cloud in Dalaam.

They return to Summers and find the passage to Scaraba. By activating a set of buttons in front of the Sphinx, Ness and company journey into a pyramid to find the Hawk Eye. With some help from Dungeon Man (A giant man-dungeon hybrid, also the technical first Chimera), they find a passage through a dark mire into the Deep Darkness. After the group combats the enemies in the gloomy swamp, including Master Barf, they find Tenda Village and its overly shy residents. Ness then receives a harried phone call from the Apple Kid in Dr. Andonuts' lab, but the line is cut off unexpectedly.

The group investigates the deserted lab in Winters and finds clues that point to Giygas' Stonehenge Base nearby. Navigating the base, Ness discovers Dr. Andonuts, Apple Kid, and several residents of Winters held captive in the deepest realms. Ness and the gang defeat a Starman DX for their freedom. The Apple Kid points Ness in the direction of the Onett Library, where he returned a book called "Overcoming Shyness". Ness retrieves the book and lends it to the Tendas, who soon become socially adept enough to direct Ness to Lumine Hall.

Lumine Hall deposits them all in the dinosaur-infested Lost Underworld where they find the final Sanctuary location, Fire Spring. Ness loses consciousness after hearing the melody and wakes up in Magicant, the colorful, dreamy world of his mind. Ness encounters everyone he has met in his journey here. They direct him to the Sea of Eden, his central conscience, where he confronts his nightmare, the last force of evil in his heart. By eliminating any means that Giygas has of controlling him, Ness gains incredible power with the help of the Sound Stone. The last thing he hears is his own voice telling him to head to Saturn Valley.

When Ness awoke, he and his friends teleported to Saturn Valley to meet up with Dr. Andonuts. With the help of the Apple Kid, he developed the Phase Distorter II after Porky stole the original. It needs only one meteorite sample to function properly. Ness travels back to Onett, which is swarming with fierce enemies, for a piece of the meteorite. Ness and company make it back with the meteorite and travel in the Phase Distorter II to the determined location of Giygas's Lair.

Ness and the others wind up in the Cave of the Past, but apart from the ruined Phase Distorter, find nothing. Dr. Andonuts and the Apple Kid arrive in the Phase Distorter III (Which originally a fail safe in case the SECOND one got stolen as well) with news that Porky had fled to the past where Giygas was. In order to pursue Porky, the four of them needed to have their souls transferred into robotic bodies since organic matter cannot survive time travel. Even though there may have been no going back to his body or friends, Ness quickly agreed to the procedure, saying that he could go it alone if needed (It was then that the others stood up next to him and agreed as well) and Dr. Andonuts set to work with a heavy heart as he put the four’s spirits into robotic bodies.

Now as robots, the four of them travel back in time and find Giygas's Lair with a deformed Porky at his side. They learn that Giygas's power became too great for even his own mind to handle, Giygas now exists as a nearly omnipotent entity without thought or reason; an "all-mighty idiot." After causing Porky to flee the scene one last time (to a different time period entirely, mind you), they attempted to battle Giygas, but their attacks were seemingly swallowed by the void. As Giygas attacked them in ways they couldn’t possibly comprehend, Ness turned to see that Paula had started praying with all her heart that someone lends them strength. As she did so, their acquaintances and friends from their journey return with prayers of their own and successfully help to vanquish Giygas, destroying the robot bodies in the process. With the war against Giygas over, Ness' spirit, along with the others, leave their battered robot bodies and return to the present to be met with a heartwarming reunion before everyone had to part ways. As farewells were said, Ness was asked to walk Paula home, opting instead to visit a variety of places before ultimately realizing he couldn’t just keep adventuring forever. Ness quickly teleported to Twoson after that realization, and said their farewells before returning home, finally telling his mom of the adventure he had been on.

A few nights later, he received a call from his dad telling him to meet him at a hotel, as well as offering for Ness to "beat up bad guys” along the way. It was then that Ness received an unexpected visit from Picky Minch, who relayed a letter sent to him from his older brother Porky, taunting the psychic to go after him. Ness simply gave a sigh, went to bed that night, and the next day he was ready with his trusty baseball bat in hand, adjusting his cap and heading off to search for the pig, making it his personal mission to explore the world again place by place to find his missing former friend.