I'm not sure as I don't know the story. Maybe it's about the girl upstairs having some sort of connection to Tanya Kach, like a friendship or a conflict.
As I don't have access to the 'the girl upstairs the Tanya Kach story', it's only possible to guess at the main idea. It could be that the story focuses on the impact that Tanya Kach has on the girl upstairs. Maybe Tanya Kach does something that changes the girl's life, or they are in a situation where they have to rely on each other. It could also be a story of mystery where the girl upstairs discovers something strange about Tanya Kach and the story unfolds from there.
Chapter 790, "Formation Night", is the clearest early answer because it turns Ziyang Palace's situation into a concrete plot event. It opens with In a Daoist temple on the outskirts of the city. and closes on He is Shen Lan's son after all, and Shen Lan used to be God Jiang's....
Chapter 674, "Staring at Shu Yan", is the clearest early answer because it turns Jiang Li's situation into a concrete plot event.
Chapter 519, "I'm Here to Participate in the Program", is the clearest early answer because it turns Zheng Xun's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Seeing that everyone who went to attack Jiang Li had failed...
Chapter 631, "It's Him Who Got Hurt, Then It's Fine", is the clearest early answer because it turns Jiang Yan's situation into a concrete plot event. The chapter gives readers a real answer by opening on To avoid making a disturbance, the next second, Zhao Lang directly...
Chapter 547, "What a bustling family you all are", is the clearest early answer because it turns Jiang Yan's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Because of the unsightly scandal caused by watching the live...
The best chapter pointer here is Chapter 3, "Madam, the eldest young master has been missing for over half a month". It opens with Qiao was still annoyed at the attitude of this unknown girl when she heard... and closes on Jiang Yan, forced into a marriage with someone he did not love, had....
Chapter 906, "Big Brother, are you jealous?", is the clearest early answer because it turns Yu Fei's situation into a concrete plot event.
Chapter 596, "Then Blow Them All Up", is the clearest early answer because it turns Jiang Cheng's situation into a concrete plot event. The chapter gives readers a real answer by opening on Jiang Li shook his head without any expression.
Chapter 727, "Can't Keep Up with the Twists Anymore", is the clearest early answer because it turns Chengcheng's situation into a concrete plot event. The chapter gives readers a real answer by opening on Jiang Li only posted one picture, but it shut up those haters.
Chapter 827, "Mystical Event Investigation Bureau", is the clearest early answer because it turns Fuhu Mountain's situation into a concrete plot event. Early on, Jiang Li's words indeed make sense.. By the end, Besides, their original intention to construct the Seven Star Feng....