You play the role of Aron/Eryn (more this in Cast), a young orphan living in a cabin in the forest with your grandfather Oron, a world-class Maker.
While you're away at the Fusion House creating your first Monstruct, your grandfather Oron is approached by three shady characters (2 men and 1 woman)named Johl, Cirt and Vayn. He welcomes them into his and, after a light lunch, asks how he can help them. The leader, Vayn asks if Oron would be willing to share his Maker Formula with them and even offers to pay him handsomely. Oron refuses. As you return home with your new friend, you find him being threatened by the group. You ask your grandpa what's happening; he tells you to run. A battle ensues as Oron keeps them busy while you escape. You run away as an explosion booms behind you blowing you into a tree. You lose consciousness.
Later, a young girl/boy finds you and takes you home. You wake up in a room you don't recognize and find out that you've been brought back to the Fusion House you just came from earlier. The owner says his niece/nephew, Flix found you in the forest passed out two days ago. You ask if your grandpa is there as well and the owner tells you the news that he was found missing, his house a complete ruin. The owner says you can stay with him and Flix, as you mourn your loss.
Later, you and Flin go to your house to find any clues to your grandpa's whereabouts. There you see a figure cloaked in black staring at the wreckage. As you walk closer you hear whispering.
"I'm sorry, old friend. I wasn't there in time to help you..."
He turns around just as you approach and you question him about Oron. He promises to tell you if you have a Monstruct Match with. After the battle, he speaks with you briefly and he leaves; you and Flin continue on your search. A flash catches your attention. Out of the corner of your eye you see a package with a letter with you name on it under a floor board. You open it and you read it. It asks you to meet your grandfather at Sunshine Island Resort.
You fold the note back and get ready to leave, determined to finish what Oron started, no matter what.
Now you embark on a journey to complete your grandfather's work. You'll face may challenges, fierce beasts and see great things that will change you forever--all while creating Monstructs of your own and avoiding the three people who attacked your grandfather.
But who was that man at Oron's house and what was his relationship with him?