Fuji's Mother used the pendant to seal the Tree of Mana from the rest of the world a long time ago when the Vandole Empire abuse the power of Mana so that nobody can come close to the Mana Tree. The pendant is the only key to arriving to the Tree of Mana.
The pendant later came into Fuji's possession. After Fuji was taken by the Glaive Empire, both Sumo and Bogard goes off to her rescue. They manage to make their way inside Glaive's Airship and they find Fuji, she gives the pendant to him while Julius demands to pendant for himself and attacks Sumo. Blowing him off the airship, and crashing through Amanda's house in Menos. While Sumo is in bed, Amanda steals the pendant.
When Sumo catches up with Amanda in Cave of Medusa, he ask her why she took the pendant. She tells him that it was for her brother's sake. She gave it to Davias in exchange for her brother, but Davias cursed him and turned him into a parrot. So she must get the tears of Medusa to uncurse her brother. Sumo gets his hands on the tears, at the cost of Amanda's life, and uncurses Lester. The both of them go after Davias within his mansion and finds him waiting at the rooftop.
When Sumo finds Fuji inside the castle, she tells him that she no longer has the pendant, and they must retrieve it as soon as possible. She mentions that Dark Lord is in his room located on the top floor and she joins him.
After Dark Lord is defeated, Sumo reclaims the pendant, but he sees that its a fake and wonders where is the real pendant is. He heads down the stairs and doesn't see Fuji anywhere. Then realizes that she must be with Julius at the Waterfalls. He rushes out of the castle and sees Fuji heading straight to the waterfall. Fuji under the control of Julius, is ordered to take the pendant and cast the spell to reverse the Waterfalls. Sumo tries to stop her, but Julius tells him that he's the last one of the Vandole Empire, and he shall receive the power of Mana again. She utters some mystic gibberish and the waterfall reverse, but before Sumo can do anything. He's blown off and fall down below while both he and Fuji ascend the waterfall.