The Left Hand of Darkness
Estraven is Ai's guide even though Ai doesn't realize it for most of the story.
In Karhide and Orgoreyn, Estraven tries to guide Ai through the ins-and-outs of Gethenian culture. Unfortunately, Ai doesn't understand the subtlety of Estraven's ways and thinks the Gethenian is trying to disrupt his mission somehow. Then Estraven quite literally guides Ai across 840 miles of barren, wintery wilderness to safety at the eventual cost of his own like.