Sukuna Is From Jujutsu Kaisen,thousand of years ago he was a human sorcerer that killed thousands and thousands of sorcerers before eventually becoming a curse spirit,he later died,however his fingers where still around,later in the present a kid name Itadori Yuji ate one of his fingers and became his vessel,He tried to take over but couldn't because Yuji will power can hold him back.Sukuna had a back plan however,He trick Yuji and took over his friend Megumi body, who didn't have the will power