Thanks for the chapter!
Manga really leaves out a lot. More details in LN. Behind one of the large posters on the wall in her pharmacy she has a small, fully equipped operating room. That's where she fully entered with the body. Not sure why felt had to hide it, maybe to avoid scaring customers or inquiries from the Marine Corp. As for the culprit I think it's a deliberate attempt not only to hide the girl's identity, but frame that ex-Marquiss daughter. Chenyu has already mentioned how MC had made the Marquiss drop out but all she had to do was find another one. So my highest bet is Chenyu as Miss Bu doesn't seem type to know much about medicine or poison and Marquiss too broke and under guard for ruining family to be paying 100 silvers each to hire instigators.
Oh dear, I wonder when they'll notice the guy has a sudden craving for brains, moaning, has no feeling in his arms and legs (they don't tan either,) can lift several hundred pounds with his right hand, run over 60 mph, see long distances and at night light wearing a night goggle, and all for the low price of 6 million silvers! Btw, Steve Austin is suing for infringement but due to it being another world with no diplomatic channels they don't acknowledge the US' copyright laws.
