
No the dude that took over cale's body is named kim rok soo. He was reading the novel "birth of a hero" where the protagonist is choi han who got TRANSPORTED from choi han's world to a fantasy world thus started the story "birth of a hero"
Cue word: choi han was "transported" meaning he did not posses anybody. Main protag of the novel "birth of a hero"
Cale henituse: soul of kim rok soo "transmigrated" and took over cale's body who's a canonfodder inside the novel "birth of a hero".
So this is like you reading an isekai novel then one day you wake up your soul took over one of the character inside that isekai nove

I suggest u to read the novel, its amazing. Although the manhwa is great they tend to skip a lot of details. Now stop trying to undestand what im saying and go to https://www.novelupdates.com/series/trash-of-the-counts-family/ and start reading the novel ╮( ̄▽ ̄)╭

maybe this is a super spoiler...
Choi Han actually came from the same world like Kim Rok Soo, both are from seoul. but when he turned 17 he was transmigrated and become the novel’s protagonist and the novel’s author is the biggest spoiler so I won’t tell. And KRS transmigrated later, but unlike CH, KRS transmigrated into someone’s body, which is Cale’s body
OK I'm confused like for real.
Did Cale return back in time?or Choi han reincarnated as Cale? Or Did someone reincarnated as Cale????