Lol. Its obv no one here has actually read the book and why it's relevant to the manga.
For those interested:
The Black Swan is a book about unknown unknowns. Basically, you are talking about events or information that you would completely disrupt an industry, business, or peoples.
The American terrorist attack 9/11 is used in the book. Because previously, airplane hijackings were seen as a way to take hostages in the 1960s to the 1990s. If you based your hypothesis on those hostage events, no one expected to use an airplane as a bomb. It was actually new and imaginative thinking to crash an airplane into shit.
For you the reader listening to this, your knowledge, perspective and information of whatever should always be considered incomplete, outdated, or wrong.
Ex. That girl you are interested in isn't shy, she already has a boyfriend you don't know about. But everyone in class knows you are super into them, and they are too nervous to tell you.
So in this case, the black swan is a DILF turning into a hot girl. Which is funny, because I would think any hungry capitalist motherfucker would take advantage of a second youth and dominate like an isekai.
Read books guys, shit will make you strong.