Project Tatterdemalion Reproduction: Male, Female, Tritiya
Yes, I lifted that last out of Hindu traditions. In this AU the kami and other species native to Shangri-La are also three-sexed, meaning the locals have that term in general use. (There are also plenty of imported non-native species on the planet besides humans who are binary gender.) So, as per Saiyuki canon, Kanzeon is not a she. Kanzeon’s a se.
(Poor, poor Gojyo.)
Meaning part of the reason Kanzeon and the sutras find the akuma virus interesting is that it goes after a binary-gendered species and makes it trinary.
Here’s how the bunnies say it works. Normal humans are XX and XY. (We’ll ignore other possibilities for the moment; they’re messy in RL, they’d be at least as messy in this setting.)
Let’s say the Arrancar took the easiest approach for dealing with sex in humans and mammals in general: mess with the X chromosome.
Going from a jumping genes (transposon) perspective, the same strand of DNA can produce very different results depending on which direction it’s “read”. So. One “control” strand of DNA inserts on an X chromosome. If it inserts “up”, everything goes normally, and you have a regular male or female. If “down”, the X becomes a W, and you have a tritiya. (W is dominant over X in a case of WX.)
Unlike kami, though, youkai and shinigami tritiya aren’t blatant hermaphrodites. There are some small visible differences, but most of what makes things work is “out of sight”. (And I’m not getting into the graphic details. There are tentacles. ‘Nuff said.) And outside of a bit of extra projective strength, it doesn’t show up until maturation. I wasn’t kidding about a sort of second puberty, and I imagine those affected are not happy at all.
(Those I know are affected on the shinigami side so far – Juushirou, Retsu, Kaien, and Yumichika. On the Saiyuki side, Kougaiji. Mwah-hah-ha….)
Note that since a lot of psychokinesis is involved in the infection itself, once one cell is infected, the rest key off that gene-strand orientation. So any one individual has X or W, not a mosaic of cells.
Also note, given psychokinesis, a youkai or shinigami may subconsciously – or even consciously, once they know more – pick “which way is up”, if they infect someone. If they’re looking for a good packleader or need that third sex, the hapless victim is, more than likely, going to end up tritiya.
As for reproductive details – without getting too graphic, it requires all three sexes to have a lot of fun, relatively close together in time. Once all the cells end up in the same womb, you have 3 combinations: sperm + egg, sperm + tritiya cell, egg + tritiya cell. These three combos then have to get together, merge – and then separate, leaving a viable zygote and disposing of anything that “won’t work”.
As you might imagine, there is a lot of psychokinesis involved, and not a high fertility rate. But if the three are a good combo, you have a chance for one, two, or even three offspring from any one mating.
(Tritiya can nurse, thankfully. That’s a lot of milk for one mother!)
(This probably does not make male-origin tritiya any happier.)
So the genetic results end up with these possibilities: XX, XY, WY, or WX. WW is unlikely because you only have one tritiya involved (it probably wouldn’t be viable, who knows). The kids look male or female at birth, you’d have to run a test to be sure.
And yes, the Arrancar know darn well this will screw with people’s self-identity. That’s part of the point.
…Did I mention that as a species, humans are stubborn bastards?