It's Holo - it was initially translated as Horo due to the R/L situation in Japanese, which has stuck with a lot of the fans, however the official translation is Holo. The Japanese license holders forced Yen Press, who translate the books in the west, to use this translation as they actually enquired due to the fan support for the original Horo translation. Her name is actually shown written as Holo very briefly (possibly for this very point) in the book 3 section of the second season of the anime.
In terms of characters you'll see a reasonable amount of a few side characters during these arcs; due to the shift in focus they play a bigger role in the events, similar to how Nora played a larger part than most in the second arc of S1 (and appears in the S2 OVA).
You're right though, it's not often you find a (what is at heart a romance) drama, wrapped up in the swaddling clothes of fantasy and economics, which is certainly an interesting or different blend. Having seen the first season now, I'm sure you probably also agree with my statement that the series IS just that, rather than some sort of pervy material as was suggested a few weeks back haha
If you do like the series, take the time to read the books if you get a chance; by and large the series is a pretty faithful translation, and a good one at that, the book however does give you more insight into Lawrence's thoughts and also contains extra details and minor scenes which you won't see in the series due to time constaints. Unlike many poor adaptations, the novels feel like an expanded, slightly more indepth version of what you see in the series, compared to most adaptations often leaving you feeling that a lot has been stripped away from the novel to fit everything in.
Edit: Just finished Tonagura. Not a bad little series actually, nothing major but overall I found it a fairly sweet little drama/comedy with its heart in the right place. Not big or clever but perfect holiday material.
Edit Edit: Whoop. My S&W BD sets have shipped. Judging by the order page both seasons 1 and 2 (Ltd Ed), hopefully I'll have them by the first week of September