This is the story of William, a tall teenage boy living in a mansion with his step sister. One day, he has a bracelet from the future, a future where the artificial intelligence: Goliath, stages as war against humanity, whom have mastered technosorcery to counter Goliath's conquest of both space and time. The magical bracelet allows William to become the Galaxy Pegacorn to defend his time from Goliath's drones to prevent mankind from utilizing technosorcery.
Teaming up with William is his tomboy girlfriend Crystal who has her own bracelet from the future: Comet Fairy. When they're not defending earth from their future threat, they spend their time at school, making new friends and enemies including the bullies that bothered both of them. Crystal will do anything to protect her boyfriend, but overtime, the bullies realize that even their hearts can change and slowly become friends.
Then, once graduated, William, Crystal and their newfound friends get onboard the Timeship Mermaid's Sword into the future to confront Goliath, ending his threat once and for all.
In the end, the group awoke back on Earth, glad that they overcome the odds and hope for a better future to come, without Goliath's creation. Though, unbeknownst to them, Goliath will find a way to come into existence. He is inevitable. So essentially, time is in an endless loop.