After Returning from Immortal Cultivation, I Found My Little Sister Had Become a Yandere?

The male and female protagonists are brothers and sisters, they are not squeamish, the writing is off-topic, and there is nothing interesting about it. The female protagonist (sister) likes the male protagonist (male protagonist), but the male protagonist is currently just a tool of the slave master. His only function is to lead to the background world of cultivation. The female protagonist attracts women, and the feeling is the same later (she blushes when a woman praises or touches her, but the slave master brother does not get this treatment). The An Ning who comes out later (seems to be non-human) is quite bisexual, and currently has an extremely close relationship with the heroine. All in all it's toxic and boring.

So is it just a setting to introduce him as a cultivator at the beginning?