Bleach is a mega-popular shonen action series that has returned for one final story arc in the Fall 2022 season, and this is a fine time for veteran Bleach fans to finally fill in the gaps and ponder some of Bleach's more obscure mysteries. Fans are about to learn much more about Ichigo Kurosaki's origins and heritage, but what about his first Soul Reaper friend, Rukia Kuchiki?
Even longtime Bleach fans know remarkably little about Rukia's ancestry and origins, as the lore hasn't explored this topic in much detail. Through flashbacks, fans know that Rukia was once a street urchin in the Soul Society's Rukongai district along with Renji, but whether Rukia was actually born there or originally born in the world of the living is more obscure. However, it raises some intriguing possibilities.
The Ambiguity of Rukia's Birth Family in Bleach
There are no solid answers on where Rukia first came from, but experienced Bleach fans know that there are two main possibilities. The first is that Rukia was born right there in the Soul Society, since souls are perfectly capable of sexual reproduction, just like humans. The best example is the noble families, such as the Kuchiki and Shihoin families, with the talented Byakuya Kuchiki having been born as a soul from day one. This vaguely suggests that natural-born souls are exceptionally strong, but there may be exceptions, such as Rukia.
For her part, Rukia may have been born native to the Soul Society, but she might also have once been human and died before her pure soul, her Plus, was escorted to the Soul Society. Her much older sister, Hisana, may have died under the same circumstances and arrived at the Soul Society at the same time, which explains how the sisters stayed together in such a big world.
In this sense, there are two "breeds" of souls living in the Soul Society, with it being a mix of native-born and guest souls who are not always easy to tell apart. During the "Soul Society" story arc, to name one instance, Ichigo's group met a young male soul named Yuichi Shibata, who Ichigo and Chad met as a Plus in Karakura Town. Yuichi had been purified after Shrieker's defeat and was escorted to the Soul Society, where he formed a found family and adopted the Soul Society's mannerisms, including his new outfit. The only reason Ichigo recognized Yuichi as a dead human-turned-soul is the fact that they had met before. Otherwise, Yuichi was just like the souls around him, some of whom might be native-born, others guests.
Perhaps the same was true for Rukia and, for that matter, her fellow street urchin Renji. Just watching Rukia's street urchin antics in those flashbacks gives no sign of whether Rukia is native or not. She'd end up the same way in either case, lending an air of mystery to her character. Were Rukia's parents' souls living in the Rukongai district, or had they been human? There's no telling, and Rukia says very little about her family aside from Byakuya, her foster brother.
The Many Isekai Adventures of Bleach
No matter what Rukia's origins may be, all this plays neatly into Bleach's isekai themes with the supernatural. While Bleach is not a "true" isekai anime like Reincarnated as a Slime or even Dr. Stone, it cleverly borrows isekai's best themes without relying too heavily on them, such as Ichigo's otherworldly adventures to and from realms like the Soul Society and even Hueco Mundo's nighttime desert. Meanwhile, Rukia is a kind of reverse-isekai character, spending a few weeks in Karakura Town in her gigai body, unable to return to the Soul Society. If Rukia were born human, then she got isekai'd to the Soul Society, grew up, then got isekai'd right back to Earth. However, even if Rukia is Earth-born, she wouldn't recognize Ichigo's 2000s-era world so easily.
If Rukia had been born human and got sent to the Soul Society along with Hisana upon their deaths, then given how long it takes for souls to grow up, Rukia must have been born many decades ago. According to some sources, Rukia is at least 150 years old in Earth time, though in terms of appearance and mental maturity, she's in her late teens or so. This means that if Rukia was born human, died as a baby, and got sent to the Soul Society, she would have been born in the years leading up to the Meiji era, probably in the 1840s or '50s.
So, even if Rukia and Hisana saw Earth life for themselves before dying, neither would recognize 2000s-era Japan after growing up in the Soul Society and visiting Karakura Town. An Earth-born Rukia has forgotten all about the world of the living, meaning she is mentally a Soul Society native no matter where she was physically born. In turn, this makes Rukia a true reverse-isekai character in Bleach, exploring Ichigo's world with fresh, curious eyes that know nothing about cars, vending machines or CD players.