Year 2021, Gi-Hun, Player 456, took the win against his friend, Sang-woo. Going home with 45.6 Billion Won, he find his mother dead in their house. Before going on a trip to the US, he finds the guy from the train station a year back. The guy he was playing with received the same card he did a year back, so he went over and stole it so he wouldn't die.
Before boarding his flight, Gi-Hun calls the number on the card and gets aggressive with the person on the other line. He turns around a signs up to play the 'Squid Game' again.
Upon his return, he notices two smaller, and oddly colored guards. A black guard with the mask of a Star, and a blue guard with the mask of an umbrella. Gi-Hun had never heard of a Star or Umbrella guard, so he was very confused.
With a few days investigation, he found himself sneaking around the colorful room and to a room he shouldn't be in. The room was dark with two dimly lit corners with beds. He heard yelling from another room, so he left to investigate. There, he saw umbrella threatening a square guard with a gun. Gi-Hun watched the whole thing play out, the square guard getting shot in the process.
A triangle guard then came out from the darkness, hugging the umbrella. "You tell me if anyone else hurts you," they said. Gi-Hun returned to the small room filled with beds. He didn't know that the Star Guard was watching him.
In the morning, everything went downhill for Gi-Hun. Star Guard would stalk him, protecting the triangle and umbrella guards. Before long, umbrella was held at gunpoint, as Gi-Hun took off his mask to reveal his face.
You don't know how or why, but you've been isekai'd into the world of Jujutsu Kaisen. Although your first instinct is to stay far away from the plot, you've been blessed with an abnormal amount of cursed energy, and for better or worse, you find yourself sucked into the storyline. You decide that you may as well use your newfound powers for the greater good, and if you're lucky, you might succeed in rewriting some of the characters' fates. But it turns out that your presence in this world is even bigger deal than you first thought, and soon, everyone wants to make you theirs.