Chobits, Ookami to Koushinryou Recommendations
There are a lot of differences between these two anime, the time, the feel, etc. but the characters relationships are similar in the romantic sense. Its a completely different story entirely, but if you liked the romantic comedy in Spice and Wolf, then Chobits is something you may want to consider watching.
Both Anime explore the relationship between a male human and a female non-human. While they are set in completely different times, I feel like the relationships portrayed in both these anime's superb.