Man

He's not realy worried sick at best he's somewhat concerd if she's dead or alive. But i would say that all the guest from the party are thinking the same. So that does not show him being worried sick

He’s not worried about penny, he’s worried that his darling sister Yvonne is going to be punished for poisoning and potentially killing an eckhart family member. Remember that Yvonne hasn’t been officially named an eckhart yet so she’s still just a commoner guest to the Eckhart family. She’s not even a noble so she has no backing. If the investigation shows Yvonne as the one who ordered her maid to poison that cup, Yvonne is getting the chopping block. There’s no trial by peers for her. He couldn’t care less about pennys health and wellbeing. He’s only wanting to clear Yvonne’s name and if she was poisoned by Yvonne’s maid and doesn’t have lasting damage, he can argue on Yvonne’s behalf saying the maid worked alone. The only ones truly concerned about her health are: pink haired bro, prince, father and bunny man.

Hmm I'm not sure if he is truly worried about Yvone or it is just brainwashing bc the things about Yvonne he could say but also i would put it past him. But i would say twhat he's concerned about is that he can't say what he want so he's really think about himself

Wasn’t everyone talking about a spoiler about how he has incestuous feelings towards the original Yvonne? That’s why I’m saying he’s worried about Yvonne. Brainwashing is just making that feeling more intense but I think he has some not so brotherly love towards Yvonne. And the reason why this theory/ spoiler is believable is because after penny talked to the pink haired bro and dad, they were both able to break the brainwashing of their own volition. Penny has also tried to get on big bros good side but never was able to. She gave up because he will never change and that’s cause on a base level, he just straight up hates her for taking Yvonne’s place.

Hmmm maybe I'm not saying no but i just didn't read spiliers so damn . I didn't think he was a good person but damn

Not exactly. The sister Derrick is romantically obsessed with is Penny, not Yvonne. Just look at that beautiful bird he keeps caged, that's a damn big clue. He mistreats Penny because he cannot own her in the way he desires.

I didn’t read the raws personally so I’m just following the rumours but I think it’s true from the way he’s acting.

Really? I read people talking about how he loved Yvonne not penny. I guess there’s just too many rumours to know which one is accurate and which one isn’t.

Bro me too we can't trust spoilers we know that he has feelings for at least one of the sisters maybe? Idk lol

Maybe you misread, or someone mis-wrote? I don't read spoilers, so these are merely my own interpretations. Clearly Derrick loved Yvonne, but the kind of natural love between older brother/younger sister. It's not the same as his strained feelings for Penny.
Let's see if in the future I'm proved wrong, but for the time being I didn't see anything incest-y towards Yvonne yet.