1. Why did you decide to give the characters Asian names? It could be a good game about the Roman Republic. The setting looks like that, and the characters look rather European. The slave girl could be from one of the Germanic, Scythian, or Proto-Slavic tribes. Maybe even the daughter of a chieftain or a renowned berserker and that is why she's so muscular. And she's depressed because her tribe and family members were either enslaved or killed. The son could gradually teach her his language, and she could tell him about her homeland. Also, it can explain the disdain he feels towards her. Let's assume that his elder brother was a Roman soldier and was killed by the barbarians during one of the campaigns.
2. Would you consider making her hair customizable? Blue hair is not natural, and it ruins the immersion. It'd also be cool if the names were customizable.
3. Many similar games jump to sex too quickly, making them dull and unmemorable because they are unrealistic. There's a great potential in this game. You can make it more psychological and, thus, more interesting. Introduce sex scenes gradually, mixing them with the plot and character development. Also, please, make her smart and resourceful. Not just another sex doll.