>>278025072The first movie had Ito's direct supervision and him working on its script, it's about as canon as you can get regarding his actual thoughts on what Tomie 'is'.
>She was once a real human girl (the Tomie in the first chapter) who got killed which spawned the hivemind abomination Tomie.Literal headcanon. The first story doesn't imply the Tomie we see was the first one whatsoever.