What the hell?
Rider and Kiyoshi both felt a wave of heat crash into them, before hearing Shuya let out an almost deafening bellow as his hair and eyes changed colour. Then, dropping Isa onto the floor without any care, he charged at the newcomer, his speed far greater than he had previously shown.
Crap, he's inverted, thought Rider.
Shuya had told her of his demon blood, and Rider was aware from Rin of some of what that entailed. Plus, he had told her previously that he needed to keep his violent impulses in check. She was unsure of what, exactly, had triggered him to invert in this way, but from the way that he was going after the newcomer he had obviously found her attitude even more grating than Rider herself had.
More worryingly, though, in that state he could not be trusted not to attack the children. Indeed, the way that he had suddenly dropped Isa indicated that he couldn't really care less about them any more. And, with Kiyoshi as he was, that meant he could be in real danger.
Rider considered her options. She could protect Kiyoshi, or she could help the newcomer. Honestly, she suspected the girl could at least protect herself against one attack, so she didn't see any reason to make a move right now. Once Kiyoshi was out of the way, then she could help defeat the opponent.
Kiyoshi, on the other hand, had nothing to consider. Summoning his swords, he prepared to jump in to protect the girl, as Rider mentally cursed the hero complex he'd gotten from his father. However, to Rider's relief, Kiyoshi's movement was not quick enough for him to be able to protect the girl.
Her relief, and Kiyoshi's, further increased when the girl pulled out a Katana.
Ah, good, she can at least put up a fight, thought Rider.
Then, the girl spoke.
"Element metal, come forth".
And, with that, a giant metal sphere formed around them, with her and Kiyoshi both inside, along with Taiga and the newcomer. Then, the girl spoke up.
"Barrier's up, I had expected to keep the casual attitude Rider but captain crazy stopped that cold, I'm Satoshi's half sister and my parents should be blindingly obviously. Taiga when this Barrier drops you and the boy there need to run for safety, I'll deal with this idiot."
The girl's statement momentarily confused Rider.
Half-sister? thought Rider.
She couldn't understand how that could be. It was obvious from her looks that her mother was either Sakura or Rin, but Shirou wasn't the sort of person who would cheat on his wife in that way, but Shirou couldn't have a child with two people.
Unless....
Oh, of course, Archer..., Rider thought.
Rider knew of Rin's affection for her former servant, so she could easily believe that, in a universe where servants had survived, they could have married and had children. And, that meant that Taiga and Sakura were, in a sense, half-sisters, in the same way as Kiyoshi seemed to consider Taiga to be his own half-sister.
Kiyoshi, on the other hand, was more bothered by the second part. He had no intention of running for safety, not when someone was in danger. He was going to stand and fight alongside this new girl who, judging by her looks, was his mother's daughter, although she was apparently also somehow Taiga's sister.
Rider, though, knew exactly what Kiyoshi would be thinking.
"Kiyo, we'll deal with Shuya. You need to get Taiga to safety, and protect her if the idiot comes after you two", she said.
Of course, Rider knew that Taiga likely would not need protecting. Her eyes could quite easily deal with any threat. But, she also knew that the only way to get Kiyoshi to keep out of the fight was to give him someone else to protect.
Kiyoshi turned to her and spoke.
"OK, Aunty Rider, I'll protect Taiga", he said, smiling.
Then, Rider turned to the newcomer.
"So, since we're going to be fighting together, I guess we should introduce ourselves.
You already know me, I'm Rider from a world where Shirou married Sakura after the Grail War. This here is Kiyoshi, their son. I assume you are the daughter of Rin and Archer, but it would be nice to have a name to call you by", she said.
