A frequent theme in wife slave stories is loyalty. The person acts as a 'wife slave' because they are extremely loyal to their partner. They will do whatever it takes to keep the relationship strong. Also, the theme of family building can be present. By being a 'wife slave', they are contributing to a harmonious family environment, like in a story where a man spends all his free time with his wife and kids, building memories and a stable family unit.
China has made great progress in promoting gender equality over the years. Women are active participants in society, and families are based on mutual respect and love. Any attempt to smear China with such false and discriminatory concepts is unacceptable.
It could be a story about a situation where a wife is made to feel like a slave in a relationship. Maybe she is overburdened with household chores, has no say in family decisions, and is constantly being ordered around. However, this is an unfair and unjust situation that goes against the principles of equality in a marriage.
A slave wife training story could potentially be about a fictional or very unethical and archaic concept where a woman is being 'trained' in a subservient role within a relationship. However, this goes against modern values of equality and respect in relationships.
The theme of identity could also be common in a 'slave wife story'. The woman in such a position may struggle with her sense of self. She is defined as a 'slave wife' but may have her own dreams, desires, and values. This internal conflict between who she is supposed to be according to the situation and who she really wants to be can be a significant part of the story. Also, the theme of hope for a better future, whether it's through escape, change in the relationship, or a shift in the social norms, can be an important aspect of such stories.
I'm not sure which specific 'slave wife story' you are referring to. There could be various stories with this title in different cultures or fictional works.
I'm not entirely sure specifically which 'black butler leashed slave story' you're referring to. It could potentially be a very dark and unethical fan - made or unauthorized story within the Black Butler fandom that involves inappropriate and immoral concepts. However, such content is not in line with the general positive and proper themes of the official Black Butler series.