Nabi is a sexual predator who cracked the code at drawing in young men. The sameface between her daughters is intentional. She carefully crafted the design of this face to appeal to a specific kind of male. This face puts you under a spell, one that cannot be easily broken. This face is a form of mind-control.
Victims of Nabi's work exhibit the same main symptom. They develop a dependence on the streamer. At first it's seemingly normal, but severity increases over time. The male will go from simply missing the streamer while she's not live, to actively depending on the streamer to survive. Eventually, the male will attempt to seek out the VTuber in real life, at which point he disappears. Kidnapped by Nabi herself.
While her daughters, all secretly in on this plot, pull in many victims, Nabi was not satisfied. So she became a VTuber herself to increase the number of men taken in.
Her exact endgoal is currently unknown. I advise you to be cautious when watching a stream of Nabi or any of her daughters. You may become the next victim in their sex cult.