In the anime The Quintessential Quintuplets, the quintuplets have halluces separated from Index toes.
Yotsuba's feet, from Season 1:
It's said that in the past, Japanese wear wooden sandals and therefore get this kind of separation. However, in the anime, the quintuplets don't wear shoes at home.
At their fancy home, from S1: In the cottage during vacation, from S2:
My guess is that they wore wooden sandals or the like back in their childhood and formed the separations. But childhood isn't very long, babyhood subtracted when one doesn't wear any shoes. Can wearing wooden sandals in childhood form a lifelong separation between the hallux and the Index toe? How long does it take to form such a separation by wearing wooden sandals and the like?
If the above idea doesn't make sense, how can a modern Japanese form such a separation?