[Ka-el]

Spoiler for 257:

Well so maybe that's why Sukuna had two extra arms, eyes and mouth, he ate his twin in the womb and maybe that's why he was an unwanted child, basically a cannibal before he was even born. Not only this, twins share cursed energy and so they are considered failure and bad luck among sorcerers. Maybe that's why Sukuna ate his twin, tso he wouldn't have been "incomplete".
Now, the doubt is about the CT, if Fuga and Shrine are separated techniques, perhaps Shrine was actually his twin's technique while Fuga was his own, or the other way around.