WARNING: The following contains spoilers for Season 2, Episode 10 of My Next Life as a Villainess, now streaming on Crunchyroll.
Katarina Claes' foster brother, Keith, sees prince Geordo Stuart as his main rival in the race for Katarina's heart. He deeply loves his foster sister, putting up with her idiosyncrasies with boundless patience. When he vanished, the Claes family was led to believe that he was fed up with Katarina and left, but the opposite is true.
In Season 2, Episode 10 of My Next Life as a Villainess, it's clear that Keith's abductors aim to break his will with insidious dark magic, the same arts that Raphael Walt once wielded against Katarina. In this new otome game timeline, Katarina Claes has become the hero, so dark magic users have taken over her role as antagonist. "Fortune Lover" must always have a villain.
Episode 10 continues the hunt for the missing Keith Claes, with an enchanted teddy bear from the Department of Magic pointing the way. Despite the circumstances, Larna, Katarina and Maria Campbell are in high spirits and enjoy each other's company on the road as friends, unaware that their mutual enemy lays ahead. After dealing with Raphael Walt, Katarina believed she had dealt with dark magic for the final time, but dark magic has actually become more persistent and is now a bigger threat than ever in the "Fortune Lover" world, and Keith is now bearing the brunt of that reality.
Elsewhere, Keith awakens once again in his dungeon cell, his spirit unbroken. He's been beaten several times already, but his faith in Katarina keeps him going -- and his captors know that. A hooded young woman activates her dark magic and explains her intent to take Keith down a few pegs and ruin him and his noble status alike. She, along with Thomas, plan to tear down the wonderful life Keith has with the Claes family -- and Keith is helpless to stop them.
Larna and Raphael Walt figure out that Keith's disappearance lines up neatly with reports of dark magic, and finally make the connection to Keith that may save his life. Larna breaks the bad news to Katarina's group, and adds that the dark magic users manipulated Keith's estranged mother to capture him. Thomas and the hooded young woman prove themselves as villains on par with the original Katarina Claes, if not worse.
All of this takes Katarina by surprise, suggesting that Keith's capture never happened in the original "Fortune Lover"'s plot. Katarina's transformation from villainess to hero warped Fortune Lover's flow of events in many ways, including the creation of a harem centered around her, and Keith's capture is the darkest consequence yet of Katarina literally changing the game. The game world naturally adjusted to its lack of a villainess by amping up dark magic's role, ensuring that Geordo, Mary Hunt and the others still have a formidable foe to face. Thus, Katarina may be indirectly responsible for Keith's capture, but she can still make it up to her foster brother with a speedy rescue.