Oba-sans, to put it in somewhat difficult terms, are life-forms that have stopped evolving. And anyone can turn into an Oba-san. Young women, of course, but even young men, even middle-aged men —even children. You turn into an Oba-san the instant you lose the will to evolve.
Ryū Murakami, Popular Hits of the Showa Era
evolve, men, oba-san, will