As described in the novel The Beetle in the Anthill, the Golovan Schokn and Lev Abalkin worked as a duo in several missions, and we know from Abalkin's report on the Dead World that he considered Schokn a friend, maybe even his bestie. Lev wrote that he 'took care of him when Schokn was sick with those strange alien illnesses and would have had Schokn's back in a brawl', but he had no idea what Schokn himself thought of him.
The question is, did Schokn return the sentiment? It's extremely hard to write 'alien' characters, but I think the Strugatsky brothers suceeded with this one. I have absolutely no idea where I stand with Schokn, and if the concept of 'friendship' even exists in the Golovan language.
Given Abalkin's very peculiar origins was Schokn working with him as an agent with instructions to observe (or perhaps even eliminate if needed) considering their associaton merely a tedious, if important duty, almost a voluntary exile from the beloved Pandora planet or was he also Abalkin's friend?