The story is a bit all over the place but here's what I gather is what happened so far:
Ciel is a reincarnated Korean woman who is now in a novel she finished back in her old world. She's reincarnated as a common maid in Duke Eckart (?) [the white-haired guy], who is a minor villain/secondary male lead.
The original novel went like this:
- Liena [the blonde girl] is the FL. We don't know who the ML is yet.
- She starts off in an engagement with Duke Eckart who she is one-sidedly in love with
- The engagement starts off with Duke Eckart out at war for 8 months and Leina grows lonely
- Because of the Eckarts' rivalry with the Visiennas [the black-haired guy's family, this guy is either the Duke or one of the brothers], the Visiennas kidnap Liena and try to ransom her for possession of Eckarts' mines.
- Duke Eckart comes back from war and rallies a force, and even gets the royal family to support him, so he goes and rescues Liena
- After getting kidnapped by the Visiennas and then rescued by Eckart, she realizes she is no match for him in terms of power, even when she is the fiancee of Duke Eckart. This is when she starts falling out of love with Duke Eckart.
- Sooner or later she falls in love or sides with the Crown Prince [ML?]. The royal family is looking for ways to limit the Eckarts' influence, so Liena decides to poison Duke Eckart. Duke Eckart dies.
- The poison she gets is extremely effective against people with high magic power, so I'm assuming Duke Eckart was a very powerful magic-user.
- Somehow she gets away with the assassination and blah blah rest of the plot happens.
- Also I assume she gets into trouble with the Visiennas again because they're all considered villains and Duke Visienna is apparently the main villain.
So this is what changes:
- Ciel decides to try and save her master because although he is a villain, he's a pretty decent master who pays good wages and stuff.
- The poison, while deadly to powerful magic users, only gives colds and fevers to those with low magic power. But there's also a 0.01% chance of activating a curse. The curse is shrinking into a child's body and possibly mentally regressing to match. Unfortunately, Ciel has bad RNG luck so she becomes a child.
- Duke Eckart realizes the truth and at some point while offscreen, he breaks his engagement with Liena
- But remember, he was also a minor villain in the novel so he decides to pay back Ciel with this convoluted plan:
- He's going to send her to the Visiennas to be their adopted younger sister for 3 years in order for the Visiennas to lift her curse; apparently only the Visiennas can lift curses
- In return, Eckart will give 30% of his mines' profit to the Visiennas for 3 years (or lend out the mines for 3 years; either way, he's using the mines as collateral)
- The purpose of sending Ciel to the Visiennas, I assume, is to raise her to become a proper lady and give her a noble background
- This is so when Ciel returns to Duke Eckart as a grown woman again, they can get engaged on the pretense that he is paying her back for preventing Liena's assassination plot
- They only need to be married for a few years because now that Eckart is single again, the royal family is trying to match Eckart with a lady loyal to the royal family to try and limit his power
- Also he'll pay Ciel very generously for all this trouble
- Oh and about the rivalry with the Eckarts and the Visiennas, the Visiennas were always powerful villains who had no real loyalty to the crown.
- The Visiennas put merit and ability over noble background so they only became aristocrats recently, so the royal family is trying really hard to limit them now
- The Visiennas would often take in individuals, regardless of background, if they were talented and make them loyal to the Visiennas
- Part of the reason why they went so far to kidnap Liena was that she was recognized by the Church (for something, it's probably divine powers) and they were trying to convenience her to switch sides
- But the Duke rescued her before the Visiennas could do so
- Also the Eckarts and the Visiennas hated each other since their father's time, and probably before that. It seems that the Previous Duke Eckart [the current's father] was a frail man who got scared easily. It seemed like there was one time where the Visienna scared the crap out of the Previous Duke Eckart and the current one is still bitter about that.
And I think that's all so far. Sorry if I got any names wrong, these are all my guesses and I'm too lazy to look back and check.