Thanks for the chapter!
Definitely a muscle brain. Should've taken butler's advice on not saying anything about things he doesn't know about. Considering Leslie's mother is shorter than the duchess in terms of genes along with being undernourished for years meaning a lack of required fuel and building material for growing it'll be a close call if she can be as tall as her sister Eli.
Why does the shop employee have a fountain pen with a pocket clip? Kind of wonder what the country's technological level is in terms of science and magic. They have what seem to be electric lights yet still use fire places to warm rooms and horse drawn carriages for distances. Yet have priests who can heal and the ritual for Eli to steal Leslie's dark magic yet haven't really shown any other magic or household type magic.
Btw, if Eli tries anything Leslie can use her shadow powers to scare her off since Eli already knows about them and doesn't want word getting out either. Also, if Leslie raises her voice the maid and Bethrion will definitely run over. Then again the Sperrado family has been full of selfish, arrogant, psychopaths with delusions of grandeur for centuries so Eli might be foolish enough to try something. After all, the main power seems to be in the silver haired children yet despite a weakened power showing up in the blond haired, green eyed children they're the ones considered showing the Sperrado family strength despite needing to sacrifice their brothers and sisters to get that power.
My guess is the Sperrado family was of lower nobility with blond hair and green eyes being favored until one of them married a powerful silver haired shadow user. After having a blond haired, green eyed kid with weak power and a younger silver haired kid with strong power the shadow user died from something, possibly complications from childbirth or an accident or something. The surviving blond parent while searching for a way to increase the power of the blond kid to associate the power with the Sperrado line found a way by sacrificing someone with the power at a certain time in a certain way with stronger success if sacrifice and receiver closely related transferring power and knowledge. So sacrificed the younger silver haired child to raise power in older blond child while teaching that only blond hair, green eyes show a true descendant of the Sperrado line while the silver haired ones are of lesser birth whose only purpose is as a sacrifice. That or only had one blond child with weak power and silver haired couldn't have more children so was sacrificed to increase the child's power. Either way Sperrado's completely ignoring fact that the power resides mostly in the silver haired and all the blond Shadow Saints stole their power from their siblings. Then again, considering how scared Eli is of Leslie's power being discovered and being the one cast out despite having blond hair and green eyes it shows how lacking in love and affection their father has for them and that considers raising the Sperrado family prestige and using them as tools to do it as more important than any fatherly feelings or concerns if any.