There aren't any arcs in Utawarerumono. Any playthrough reads everything the game has to offer. And he bangs all the women except Aruru and Kuya (although their night meetings get prety moe)
I'm gonna vote this down for spoilers because I forgot the spoiler tag and can't ever find the documentation.
Kuya concvinces him to start thinking about making an heir.
He gets Eruru because she's obsessed with him and he likes drinking a lot. The anime covered Karura's scene pretty well. After he asked if she'd die for him, she says they have to make fuck to give the contract a basis. Some dom/sub thing going on too. Yuzuha (as I _recall_ she was the last one, but I couldn't read the first time I played) wants to have Hakuoro's heir so she can finally make a contribution. She feels bad that everyone is always caring for her and she doesn't really do anything except be blind-moe and tease Oboro.
I thought the spoilers tag was just the word spoilers with a triangle bracket on either side, then the word spoilers with an upper-right to lower-left slash just in front of it, also surrounded by triangle brackets when you want to stop having your text blacked out. (Why is this so pedantic? Because I think that actually writing it out would actually produce the effect without explaining how.)
Well, I suppose that's "noble" of Yuzuha. I haven't seen the whole anime, though. Still, I do agree with your earlier remark on that drunk Touka picture; it is kind of pointless to bang Eruru and then have Kamyu suck you off in the same arc--it really makes you wonder if there was ever anything real between Hakuoro and any of his "partners."
Thanks for being so generous with the info. In your view, which of Hakuoro's "partners" did he value the most?