[[WMG: Fubuki is Shinrei's [[LukeIAmYourFather father]].]]
Look at the hair, people. Just look at the hair.
* Poofy, silver hair that no one else has: Check.
* Power(s) related to water: Check.
I know we "saw" Shinrei's father in flashbacks but: 1)We also saw Fubuki pretending ''not'' to be someone's father [[spoiler: ie, Tokito.]] 2) We never saw that guy's face, and 3) nor were he and Fubuki ever in the same room.
[[WMG: Fubuki's undead cat is Hishigi's cat]]
1) It looks like Hishigi, come on.
2) [[http://static.tvtropes.org/pmwiki/pub/images/early_hishigi_designs.jpg This concept art]] shows the cat in question at Hishigi's feet.
[[WMG: Shihodo is Kyo's mother. UNMARKED MAJOR SPOILERS FOR END OF MANGA]]
And a True Mibu in hiding, possibly limiting her power somehow in order to keep under the radar. Kyo's father could be either the Sendai Aka no Ou (with Shihodo letting Kyoichiro think that he is the source of Kyo’s True Mibu blood while it’s actually her) or another True Mibu who somehow died.
Shihodo is ''ancient''. She is stated to be several thousand years old, and yet she's never exhibited any sign of the Death Disease, a latent defect in the Battle Dolls' genetic code that can surface at any time. We've never seen another Mibu even close to her age except for Kyoichiro, and it's never even outright stated that ''he's'' older than she is. It seems very unlikely based on context that a Battle Doll would have survived the millennia she has.
The strongest argument against this WMG is Shihodo's severe curb-stomping after she let Muramasa and Kyo leave the Mibu, but it's pretty well established that Hishigi is ridiculously powerful and he wasn't even dying then. And again, keeping under the radar. We're also shown Shihodo taking a dive against Kyo and then effortlessly overwhelming him when he pisses her off enough.
She obviously knew True Mibu, because they didn't die out completely until after Kyo was born. And it is (or should be) one of the biggest questions of the fandom: where the hell are Kyo's parents? If the True Mibu were so powerful and only one or two remained, how did they die?
[[WMG: Kyo was sent forward in time to save the Mibu. UNMARKED MAJOR SPOILERS]]
Kyo just kind of appeared 22 years before the beginning of the story. There is no mention of him actually being ''born'' within the Mibu clan, and he arrived just as the Mibu Battle Dolls stopped being able to have children. The Shodai Aka no Ou calls Kyo his "final son" and the last scion of their people. Calling Kyo his son may or may not be figurative, but it's possible that he sent Kyo forward as a child so that he would grow up outside of the brutal world created by the True Mibu.