To start with, if all the subjects are noble children left behind by their family, why pair them up and have the child that remained pick between 2, of which one is related and the other isn't? How come they are not delegated by blood relation from the beginning, if being related is so important? Why even rank them in the first place when that seems useless. It also doesn't seem like a smart idea to only have 2 children, which seems to be the case for most nobles, as you won't have an heir in case the one who is actually being raised as your kid dies or falls ill. The brainwashing of themselves is also weirdly executed, especially on the ex friend slash sister slash cousin -unclear because they use it interchangeably- who is now cast into the role of a snake, which falls flat with the previously established characterization, and instead of being a point of surprise it's just annoying due to how badly it was forced. To point out another thing, if he was supposed to become his brother's slave, how come another noble got him as their pick? Too many plot holes.