Ryo knows that Mizunokuni is one of the four dominant nations of the Daitoshi region of Shibayama. Historically they've not gotten along well with their neighbors (neither have the other three) and most of Daitoshi's history involves at least two of the four nations being in some form of war with each other. Three times this flared up into larger wars, involving three or all four of the nations. Mizunokuni is based on an archipelago off the coast, and devoted to the veneration of the water Kami. Has a lot of water Wu Jen and Shugenja. Run by some sort of combination of non-hereditary monarchy and gerontocratic theocracy.
He knows that six years ago there was a revolution and that it was found out, in the aftermath, that the deposed tyrant was being dominated by an Illithid, who was also killed by the revolutionaries.
Akemi is 33 years old and a water Wu Jen. While well-off, her family was not nobility. Akemi was involved with the resistance/revolution for most of her adult life and personally led the attack that killed Kanagawa (the former Daimyo) and the Illithid. She has no living family, her father having died during a war, her mother having been taken by Kanagawa's agents, and her brother - a leader of the revolution himself - having been killed during the revolution.
Due to her status as a national hero after the revolution, she ended up being chosen as the Daimyo to replace Kanagawa. She's attractive and rather wild - as Rin implied - although she does have a preference for men. Despite her amazing looks, she's rather sensitive about her age. Due to her actions in the revolution, her status as a Wu Jen, and her actions as Daimyo, she's generally well-loved by the people of Mizunokuni. Her looks probably don't hurt her in the popularity department, either.
Haru knows that Mizunokuni is a large nation in the Daitoshi region of Shibayama based on an archipelago. He knows literally nothing of it's non-legendary history.
Haru knows that according to legend Mizunokuni - along with the three other Daitoshi cities (Hinokuni, Kazenokuni, and Tsuchinokuni) were supposedly founded by the possibly mythical priest of the Way known only as the Master of the Five Paths (or similar titles). According to myth the Master had somehow mastered all five of the elements utilized by Shugenja, rather than the one or two most Shugenja master, and personally negotiated with the Kami the pacts that would allow for Southern Wu Jen to do their thing. Supposedly the four cities sprang up at the sites where these negotiations took place, founded either by the Master himself, or by his disciples. As a result, Wu Jen and Shugenja are very common in the four great Daitoshi nations, and veneration of the Kami is even more pronounced and dominant than in other parts of Southern Izumo.
All Haru knew about Akemi was that she was the leader of the recent revolution (of which he knew the general details, given that it involved an Illithid) and that she was supposedly a great water Wu Jen, surpassed in her skill only by her beauty.
"A vacation it is then, lovelies. Say hi to Akemi for me, and do let her know that I'd love to see her again." Rin laughed.
"If anything comes up with the Cao investigation, or the Yagyu situation, I'll make sure you''re informed."
She smiled. "If there's nothing else, though, and you're not going to fuck me, maybe you should just go and start packing stuff for your trip?"