Not sure if it technically counts, but I'm fascinated by the transition from "misses" styles to adult women's in the late 19th and early 20th centuries. It was a lot more subtle than people often think - while "wearing long skirts and putting your hair up" was a rite of passage, there was still another rite of passage to go through to get to adulthood and actual eligibility.

For instance, look at the women's dresses in an ad from Charles Stevens & Bros. in 1909, and then the companion misses' (and small women's) suits ad. The misses are still noticeably girlish and have yet to undergo the rite of passage of losing their hair bows, or of getting skirts that cover most of their shoes. You can see a similar subtlety in this advertisement for sweaters: the two misses have bows, the women do not.

There's also this 1906 advertisement: the close-up miss has her hair up with a giant bow on it, while the women wear hats. The younger girl's hair is completely down with a big bow on it, and her skirt is also way shorter, up to her knees - we can't see the miss's, but it would likely come to the top of her shoe or her ankle.

Another one - commencement! Here's a portrait of the Glens Falls Academy class of 1925 in commencement attire, here's the 1920 class, and here's probably the 1900 or 1901 class. It was traditional for girls to wear white for this rite of passage, and still is in some places.

When it comes to Japanese history, people are fascinated with the image of the samurai committing seppuku. That naturally extends to curiosity about what samurai women did. Curiously, every article or popular history about samurai women seems to draw on the following paragraph from Inazo Nitobe's The Soul of the Samurai.

Girls, when they reached womanhood, were presented with dirks (kai-ken, pocket poniards), which might be directed to the bosom of their assailants, or, if advisable, to their own. The latter was very often the case; and yet I will not judge them severely. Even the Christian conscience with its horror of self-immolation, will not be harsh with them, seeing Pelagia and Dominina, two suicides, were canonised for their purity and piety. When a Japanese Virginia saw her chastity menaced, she did not wait for her father's dagger. Her own weapon lay always in her bosom. It was a disgrace to her not to know the proper way in which she had to perpetrate self-destruction. For example, little as she was taught in anatomy, she must know the exact spot to cut in her throat; she must know how to tie her lower limbs together with a belt so that, whatever the agonies of death might be, her corpse be found in utmost modesty with the limbs properly composed. (p. 141)

The bestowal of the dagger and the instruction in a proper death form a grim rite of passage from girlhood to womanhood. Or did they always? Despite being quoted everywhere, Nitobe - the 20th century writer who pretty much invented the concept of 'bushido'- was a romanticist with an agenda: trying to relate the traditions of Japan to Western ideals.

Samurai women did often have daggers, given to them to mark the transition to womanhood. In dangerous times, they could kill themselves. But samurai history covers hundreds of years of both peace and war, and a huge country with varied local traditions. Here's a much less grim, in fact, rather heartwarming version of this rite of passage, from 1860s Mito Domain, between a father, Enju, and his young daughter, Chise:

Some girls carried a small woman's dagger and some did not. Chise received one as a reward for not showing any fear when Enju took her and her brother to see a tiger some traveling entertainers had brought to Mito. 'You're a brave girl, so it should be all right to give this to you: Enju told her. "I wouldn't if you were weak."

However, no one told Chise under what circumstances she should use the dagger or explained how, should it be necessary, to stab herself in the throat. The point of giving her the dagger seems to have been to encourage in her a sense of self-assurance, a conviction that she was a strong person, not the sort to be treated lightly by others. It was not given envisioning a specific exigency in which it would be necessary to use it on oneself or on someone else. The age of Warring States was long past and people did not imagine that women might actually have to defend themselves from danger.

• p. 29, Women of the Mito Domain by Kikue Yamakawa, translated Kate Wildman Nakai

You know in the Sun Dance, when the raw-hides tore through Rain’s flesh too quickly, Sitting Bull claimed that he had had no fair test of manhood and Rain bade Bull give him a test. The medicine man cut deep through the back muscles and passed the rawhide thongs through the slits, and they hanged him high. There he swung for two days, singing his war-chants and boasting of his bloody deeds — he boasted of murdering a couple of white men, a veterinary and a sutler, straggling from General Stanley’s expedition, and thereby hangs a tale, and Tom Custer’s doom was written in blood. At last they bound buffalo skulls to his feet, and by terrific efforts, the young brave tore free, rending the flesh and tendons in such a way that for years he had depressions as large as a man’s fists in his back. But his boasts had been overheard, and Little Hair — Tom Custer — arrested him and threw him in a guardhouse to await execution. White men imprisoned there helped him escape. He sent Tom Custer a bit of white buffalo hide, with a bloody heart drawn on it with the artistry of the Sioux. It was his way of saying he would eat the white man’s heart when next he met him.

• Robert E. Howard to H. P. Lovecraft, 9 Aug 1932, Collected Letters of Robert E. Howard 2.410

This was a variation of a story about Rain In The Face, a Lakota who fought at Little Bighorn, and whose story was famously spread and expanded upon in tales of the West; told with Howard's usual relish and embellishments.