This paper presents an account of a Sakhalin Ainu (also Enciw‘itah, isolate, Russia and Japan) construction that semantically encodes an agent-patient interaction and that is characterized morphosyntactically by the expression of the agent with an oblique. In the analysis to follow, this construction is named ‘impersonal passive’ by analogy with a structurally and functionally similar construction attested in the Southern Hokkaidō dialects of Ainu. Keeping the main focus on eastern dialects, the paper takes a primarily semantic approach to the East Sakhalin Ainu impersonal passive and underlines a number of striking structural differences with the Hokkaidō counterpart. In addition, it will be argued that in the north-eastern dialects of Sakhalin Ainu, the impersonal passive can be described as an object-individuation construction ( oic ), which marks a patient object as referential and definite and has the pragmatic extension of overtly flagging the topicality of this object at the discourse level. As such, the oic compensates for the lack or non-obligatoriness of overt marking for definiteness and topicality in Sakhalin Ainu. The present paper adds to our knowledge on the still under-described Sakhalin variety of Ainu and to our understanding of the verbal and nominal semantics of Ainu more generally, which to date remains a largely unexplored topic.