rumors and gossip and the news in general can affect market values of publicly traded companies in the real world; it's the market itself reacting to things trending in online spaces.
Because the Shiunji Company is tied directly to their family, anything that causes a stir online regarding them specifically will end up reflecting on the company that shares their name - whether the rumors and gossip is good or bad, determines whether the knock-on effects on the market valuation of the company are good or bad.
The "oh, the kids of this very big and powerful family company are actually all adopted" is something that would make waves on social media (as we saw in this chapter), and that leads to questions like "why is this only coming to light now? Were they hiding it before? Why would they do that? What else is the company head hiding?" and that sequence of rumor creates uncertainty and potentially distrust as it disseminates through social media; and one of the side effects of social media in this day and age, even in the real world, is that stuff that trends on social media that is tied to public companies, will affect their stock valuation in some way.
One example is stuff like boycotts enacted through social media; if a company does something that gets lambasted online, people call for that company to be boycotted, and that results in the stock falling as the company's image and credibility takes a hit. But stuff like a recall of defective products can also result in a dip in market value, because of the perception of a bad quality or unsafe product getting reported on and spread around via news online and off reflects on the company, and then again in the company's position in the market.
So if people are suddenly questioning the reasons for the Shiunji Children's adoptive status being hidden for so long, then they might start asking about what else might be hidden away, thus creating that sense of distrustfulness and opaqueness in the Company's image, which in turn means its stock valuation will take a hit because of that negative perception.
It's all kind of volatile, and there's a ton more to it; I looked for a few studies done on the phenomenon, but it gets rather granular and technicaly beyond these super broad strokes.
