Danny Phantom - Jujutsu Kaisen fusion idea:
Jack and Maddie Fenton somehow got their hands on a Death Painting Womb to experiment on, and their work led to it fusing into their son Danny, granting him its half-cursed spirit physiology and blood-controlling sorcerery.
Additionally, another project of theirs led to a horde of cursed spirits being unleashed on Amity Park and its surroundings. And since jujutsu sorcerers are uncommon in the US, it falls primarily upon Danny to use his powers to protect the local citizenry.
Jujutsu sorcerers being, for the most part completely absent from the US, forces Danny to not only handle the curses on his own, but also gives him no way of knowing anything about them. Outside of what his parents know of course, but they might not be of much help since they mostly deal with ghosts.
So imagine a group of Jujutsu sorcerers find out about an increase in cursed spirits in some nowhere town in the US. They of course go to investigate and deal with the issue, but when they arrive some kid in a NASA tee shirt and messy hair seemingly got there before them.
Not only that he clearly is a sorcerer but has no idea what that is when questioned about it, and has most definitely made up his own silly names for techniques that have been known in sorcerer families for centuries.
Danny could probably get his own unique technique, but I think it's funnier if he thinks he's coming up with unique things that in reality has been passed down for generations by people he doesn't even know exist.
