Whether the method is All for One/One for All, the act of transferring a quirk also transfers a copy of the owner's consciousness/soul. All for One dreams of the owners of his stolen quirks because they likely live in him like the Vestiges live in Deku. So now Shigaraki is slowly being hijacked by a Vestige copy of the soul of All for One. (I say Vestiges are copies because they are independent of their original owners)
Veritas
2022-12-03 23:29:57 +0000 UTC
Soooo did we forget about Assassination Classroom? >.>