Itou Junji Kyoufu Manga Collection - Vol. 3 Ch. 4 - Dying Young

[MangaDex]

 

[Meduchi]

The story is kinda cool but the "explanation" is so dumb it drags it down.

 

[Vainfire]

Date-based fears always age poorly; see all the people worried about 2012. I'm not too keen on the gendered aspect of the sickness, seems basically unmotivated. There's also no clear reason for why Ayako remains free, why the illness develops the body into a shape strictly conforming with a culture's beauty standards, etc. Just "the end of a century".

 

[fennec]

There really isn't an explanation, just theories that no one can prove. That's part of what I like about this one and Itou's earlier work. There's not always an explanation for why stuff happens, and in horror that can make it even scarier. The girls themselves are reacting to their fear of the unknown in-story by trying that rumor because they have no other ideas.