"Sergei Goralick doesn't much like strangers banging on his door. Especially when those strangers are asking him questions. In Russia, when Sergei was young, it happened plenty. " (Keret 2)
Sergei is apprehension and mistrusting towards strangers, He resists Yoni's advances into his home and mind, when he knocks at Sergei's door. Sergei is suspicious of any individual who knocks upon his door as the KGB once did.
"The boy didn’t come for television, what he came for, specifically,is to snatch Sergei’s fish, to steal it away." (Keret 3)
Sergei's suspicion escalates when Yoni approaches his valued companion. Sergei's negativity towards his intruder peaks with the murder of the boy he perceives as acting with malicious intent, intent he had experienced in his youth in Russia.
"Anything, the Russian said [to Yoni], not to be alone." (Keret 4)
Sergei's decision of whether to save Yoni is revealed and demonstrates how Sergei takes a step back and shifts his perspective of the boy he assumed to have ill intentions. Sergei ends up losing his companion to save a life, which he took when he acted rashly; showing how his perception of Yoni changed.