Tbh, I feel like she actually does know more of what's going on than we do, kind of like the situation with that lady in the painting thing.
I also feel like maybe this older brother isn't exactly WITH the shadow, but was probably AT LEAST manipulated by it. The situation clearly seems like something that was created to force her to go to that tower (I'm not sure if that's the key part, but definitely to go there before she uses that sword to get what she needs) and perhaps kill that thing- which again, seems like a trap, especially with the 'protagonist' mentioning earlier that he thought the monster seemed 'beautiful ' based on the description.
I'm not sure about the blondie though. It feels a bit too suspicious to say that she is actually dead even if we kinda saw it. I wonder if she also has clones or something? Especially since what was she doing inside when we saw the shadow catch her outside earlier...?
But yeah, other than having a bit more faith in mc, I mostly agree with you

lowk this is a follow-up to the other comment; but everything that’s been revealed has been so jarring and off… it feels like a lot of fake info and traps ngl. especially the conveniently “learned” and “remembered”, older brother-like character. while the FL didnt a good relationship with him, it wasn’t fully hopeless one. he managed to use this position and knowledge, in like what 2-4 chapters btw, to get the FL to believe him more and push away current Yue-MC guy. ESPECIALLY with the blood sword part, craziest red flag in this story rn imo. but since this is something directly related to her existence, shes slow on realizing the probable trap. not hopeless tho, she knows something is “off” rn and her murder charge is probably a way to distract her from putting everything together… probably. I’m just spit-balling here.
using the cave story; the shadow guy and older brother guy would be like potential ppl who live outside the cave and don’t want FL to “join” them, trying to kill her I think
but on the other hand I don’t think the new older brother guy is with shadow guy, he clearly wants it gone for unknown reasons. he actually never expressed any goals to the FL except for wanting the shadow guy gone. the passive, “ ik a lot but didn’t really try to do shit” guy suddenly wants shadow guy dead? sure it’s suspicious but hes not keeping that same attitude to Yue-MC guy who by default is suspicious