help me find this pls

pretty sure it's a manhwa
fl isekais into a horror novel (?) where ml is a rich, sickly, hidden serial killer (?) fl is a maid and the system "helps" (more like sabotages) her with rewards
i remember once she got a pillow that helped her sleep better so she could boost her maid skills but then the system took it away from her
i think ml finds out that fl knows he's a murderer
fl has brown hair i think ml is blond