Kenjaku thanks Sasaki because she was Yuji Itadori’s friend and a key part of the life he led before becoming Sukuna’s vessel, and that moment is used to underline his twisted “parental” connection to Yuji.

What Happens in the Scene

  • During the Culling Game setup, Kenjaku appears to Sasaki (Yuji’s old Occult Research Club friend) in a dream‑like space and offers her a chance to safely leave the barrier.
  • As he leads her out, he unexpectedly says something like: “Thank you for being friends with my son,” clearly referring to Yuji.
  • Sasaki is confused but immediately thinks of Yuji, realizing the “son” is him.

Why He Calls Yuji His “Son”

  • The manga and supplemental explanations make it clear that Kenjaku used Yuji’s mother’s body (Kaori Itadori) as a host and engineered Yuji’s birth, making him effectively Yuji’s “mother” and one of his two “fathers.”
  • That line to Sasaki is a quiet confirmation of this parentage: he isn’t speaking figuratively; he is literally the one who orchestrated Yuji’s existence.

Deeper Reasons Behind the “Thank You”

Fans and commentators usually circle around three overlapping interpretations:

  1. A rare glimpse of genuine attachment
    • Some readers think this is the most sincere Kenjaku has ever been: he takes a moment, with a random non‑sorcerer, to acknowledge that Yuji had a normal, happy school life and someone who cared about him.
 * In this view, Kenjaku respects Yuji for turning into the “perfect vessel” and feels a twisted sort of pride in him.
  1. Recognition of Sasaki’s role in the plan
    • Sasaki and the Occult Club were the ones who dragged Yuji into the cursed object situation with Sukuna’s finger in the very first episode/chapter.
 * Some fans argue Kenjaku’s “thanks” is more like an acknowledgment that she unintentionally helped push Yuji into position to become Sukuna’s vessel, advancing his long‑term plan.
  1. Psychological and thematic effect
    • Kenjaku shows kindness, apologizes for the Culling Game having “no honor,” and offers civilians a way out, which clashes with how ruthless he really is.
 * Thanking Sasaki for being Yuji’s friend amplifies the horror: the mastermind casually reveals he’s Yuji’s parent while treating the world like a lab experiment.

A common fan take blends these: Kenjaku doesn’t “love” Yuji in a normal way, but Yuji is more than just a disposable tool to him—he’s a successful creation he’s oddly fond of, and that leaks out in this one line.

How the Anime (Latest Episode) Frames It

  • Recent coverage of the newest anime episode notes that the scene is staged to be unusually gentle: Kenjaku guides Sasaki out, speaks politely, calls the game dishonorable, and then drops the “thank you for being friends with my son” line.
  • This framing highlights how unsettling it is that someone who engineered Yuji’s birth and unleashed the Culling Game can still speak like a reflective, almost sentimental parent for a brief moment.

TL;DR (in‑universe and meta)

  • In‑universe reason: He literally considers Yuji his “son” due to having created him through body‑hopping and thanks Sasaki for giving Yuji a normal, friendly life before everything went to hell.
  • Meta/story reason: The scene confirms Yuji’s parentage, humanizes him through Sasaki’s memories, and makes Kenjaku even creepier by mixing parental language with cold experimentation and mass murder.

Bottom note: Information gathered from public forums or data available on the internet and portrayed here.