I'm sorry but you said it yourself he's heavily brainwashed! How would he be able to break out of it so easily? I mean look at Eckles and the maid. Eckles yeah he broke out of it eventually, but that's because he have STRONG obsession for penelope. Derrick not as much and that's totally fine.
I don't think I understand this obsession term because the other brother was also brainwashed for a short time but he snapped out of it and seemed sorry for his actions. Why is the older brother less obsessed when he's even keeping the bird he gifted to Penelope?
Uhh sorry for not making my point clear lol!
For me at that point of the story when Yvonne came back, Reynold already like Penelope and appreciate her so when Yvonne tries to implies sth bad towards Penelope he will likely defend her sth of that sort. (View her as good-> not easily manipulated)
Eckles is obsessed like just crazy towards her so he can't break the brainwashing too, at the same time is the brainwashing is worded in a way where Penelope will benefit he'll follow. (Obsessed anything about penelope will do-> easily but also not easily manipulated depending on method)
Derrick on the other hand. His feelings for Penelope is still mixed not yet love not much hate. Derrick feeling of guilt toward being the cause of Yvonne disappearance probably cause him to be easier to be manipulated. (Insane guilt towards Yvonne+ a tad dislike towards Penelope -> easily manipulated)
Sorry for the long read
Ah yea now I understand more, reminds me of all the small stabs Yvonne made with her comments to Derrick, Kinder felt bad for him there. Thanks for explaining your point for me ヾ(❀╹◡╹)ﾉ~
I know he's heavily brainwashed but bro is so god damn weak that he can't snap out of it even after witnessing an innocent woman getting poisoned. Everyone else could easily see how dire the situation was but this bro just stood there being stupid