Time Lords are involved somewhere, somehow
I mean, come on- we have time travel, multiple characters who could be said to have regenerated ( Suzuka to Karin, Kirihiko to Jin, Kazuto to Kazune
), and multiple significant events take place in Britain. Obviously, the power of the gods is really Time Lord technology.
And now that that's out of the way-
... is British or part British.
She's the only apparently japanese character whose hair isn't either black or close enough
to a normal japanese hair color.
Rika used the Seeded Chronos Clock to trap Karin in an alternate timeline pased on previous events, but with some modifications to make sure Karin wouldn't win against Kirihiko the second time- and if she couldn't beat him again, she wouldn't be able to come back, possibly dying in the attempt.
Such changes include her getting trapped in the "labyrinth" (what I'm calling that Place Beyond Time, for lack of a better term) due to a Seed of Chaos blocking the exit, and removing Ami from the picture so that she and Kazune would never recieve a certain vital piece of information regarding the Himekas. The boys interfere to undo Rika's acts, getting her out of the labyrinth in episode 8 and delivering Kazuto's research notes in 22.