She was waiting for us at the food parlor, as we didn't go there, she came to the baths.
She probably was waiting for us for a long time, and had, in her mind, planned the encounter to the last topic... then comes the other samurai and brakes her plans...
You close your eyes in contentment and simply allow yourself to soak. It has been a long journey to reach these lands, and ending your travels with such a refreshing bath is wondrous indeed. Truly, the hospitality of the dragon is a grand thing if they can provide such treatment for their guests. Drowsiness takes you slowly, and as you slouch deeper into the water you feel nothing could take away this pleasant experience.
"Is someone there?" calls a light, feminine voice from across the partition. "I can hear you on the other side of the room."
"Yes," you respond, relaxing and settling back into the bath. "I'm sorry for disturbing you."
"Oh, that's fine," the woman responds. She sounds about your age, perhaps a little older. "I really wasn't disturbed, just surprised. Most people aren't in this bath around this time."
You lean your head back and think for a bit. It's the afternoon, but still a few hours till evening. If anyone was going to clean up they'd have likely done it before now, and it's still too early for an evening wash. For a bath located a fair distance away from the main castle, it would only make sense that it would be so empty.
"I suppose that's why the servant led me here, then," you say as you continue to exult in the heat. "So that I could rest in peace after my arrival."
"Arrival?" the woman asks. "You're from outside the castle?"
"I am indeed," you answer. "My name is Hiruma Sosuke."
There's a splashing sound from her end, as if she stood up straight quickly. "The hero of the Battle of Skulking Shadows?"
Your brow furrows at the woman's words. It wasn't so strange for Shinjo Wanli to have heard of you, considering the realm of the Unicorn is not too far away from Crab lands. However, the Dragon are a good distance further and more isolated as well. It wouldn't surprise you that the various Daimyo have heard of your part in that conflict, but a random Samurai in a bathing room?
It's a strange coincidence. Then again, you already knew your fame had spread further than you'd originally believed. It's been years from that battle, and you haven't exactly been avoiding attention in any of the cities you've visited. Even still…
"I'm honestly quite surprised that tale has spread so far," you say softly.
"Oh, you are quite well known, Hiruma-san," she responds. "Everyone in the castle has been following rumors of your caravan for some time."
"They traveled so swiftly?" you say, grinning. "Well, I hope you've not heard anything too terrible."
"News of your travels is filled with nothing but excitement and honor, Hiruma-san..." she says, trailing off before making an embarrassed squeak. "Oh, please forgive me, Hiruma-san! I completely forgot to introduce myself. I am Mirumoto Hanabi."
Based on everything we're seeing here, it is mildly implied that she was in the bath before we were, and fairly strongly indicated that she didn't know it was us (or even particularly suspect that it might be us) until we told her our identity. This would suggest that either she was telling the truth, or that she has a Sincerity (lies) skill high enough to fool us. It also implies that her Sincerity (lies) skill is high enough that she's willing to integrate it into a plan that involves lying to someone she strongly wishes to cultivate, when she knows it would reflect poorly on her if she was caught, and she'd have a number of other much less risky options for doing the same (like, say, meeting us outside of the baths, gushing over how awesome we are, and offering to show us around, which would likely have achieved much the same objective).
Basically, the "this was a set-up (by Hanabi)" hypothesis requires that she be an excellent liar, that she be at least reasonably well-informed about our movements, and that she choose an overly complicated plan with serious potential points of failure, when a simpler and surer plan would do.
Also, based on her tactics during the discussion... she doesn't seem to have particularly good courtier skills. She has some skill at insulting someone badly enough to get them into a duel while still remaining deniable (a crude technique, directly applicable to her inferred role as a trained duelist), but it wasn't particularly smoothly done, it didn't take the wider social situation into account, and it was done as a reaction to losing position in a conversation when other uses of social skills would have let her regain that position far more smoothly, if she'd had them available. Also, "deniable" (what she achieved) does not equate to "convincing" (which she clearly did not). She does appear to have trained Sincerity to some degree, given how she pulled the insult off, but I strongly suspect that her Awareness is 2, which means there aren't any real plausible builds where she has "Use Sincerity (lies)" as a proactive skill to build plans around, rather than a reactive one, that you use because sometimes you need it.
I suspect... I suspect that there's a bit of genre dissonance with reality here. The thing to realize - you're perceiving her as a psycho %!$&#. You are correct. The dissonance here is that you're thinking with real-world instincts, where essentially all of the psycho %!$&#es are manipulative psycho %!$&#es. Therefore, you are immediately looking for where she's being manipulative. I'm pretty sure she's not. Mirumoto Hanabi is instead a bloodthirsty psycho %!$&# (at least according to best available information). That's not necessarily better, but it is different, and the one doesn't particularly imply the other. Indeed, assuming that she's a bloodthirsty psycho %!$&# makes it less likely that she's manipulative, as her skill with the blade makes the courtier skills that she'd need for also being manipulative less necessary in many cases, and learning both takes additional effort.
Obviously, we have very little in the way of hard and fast information here, but leaping to the conclusion that she directly is being manipulative is leaping to a conclusion that's actually reasonably unlikely.
/*****************/
Now, there is the other idea raised by
@EtchedSteel... that she was guided to meet us there, by some superior that knew (roughly) how she felt about us, wanted to attach her to us for reasons of their own, and did so without telling her. That... is actually plausible. It's a bit odd - they'd have to have some reason to wish to attach her to us, one way or another - but given that, it's a plausible technique, and there are certainly courtiers within the walls of the home of the family that does diplomacy for the dragon clan who'd have the skill to pull it off. It might have been done to get further information about us. It might have been done in an attempt to set up this rising star among the Crab with a Dragon Clan wife (and hopefully have her not dishonor them all by going completely psycho later on down the line)... there are certainly plausibilities here. Still, as far as dealing with her long-term goes, there's a big difference between her being used as a pawn by her superiors in subtle courtier games, and her trying to play us herself.
It wouldn't have to be some sort of Shugenja thing, either. They almost certainly knew exactly when to expect us to arrive (for that, they definitely have shugenja, and the word was spread around those who they'd want to have know). At that point, they can adjust her schedule through subtle tweaking of tasks, and influenced her to go take a bath at the right time (or known by her habits that she would). At that point, she's int he baths with the correct timing for us to arrive from the road, dusty and tired. If none of us choose to take a bath immediately, it's zero cost. If anyone else from the party goes, they could be pretty sure that she'd attach herself to them in an attempt to get closer to us. Having us go ourselves was a bit of luck for them, but not unreasonably so. Pulling stuff like that would be entirely within the skillset of a courtier of medium to high insight. Now, I'm not saying it happened that way - it would imply that a courtier of the right level of skill cared enough to set something like that up, and the "pure coincidence" hypothesis is still entirely plausible, but it might have.
