[@Ryougu] Mata is fine but this scenario will definitely not help her. She specializes in picking off enemy masters, and stunning people. But the second the jig is up she's pretty screwed which means she's at a disadvantage when most of the Grey faction is funneled into their castle. I would go with someone stronger (like for example Okita Souji) but she is allowed. For double cross you can make up an effect for it to suit it, or just ignore it.

[youtube]https://www.youtube.com/watch?v=ToYHRONiJ74[/youtube]

This video should give you an idea of how things work with her.