In Milisuthando Bongela’s self-titled documentary, which spans 30 years of her life, memories are slippery, fragile, and even dangerous. Born in apartheid-era South Africa, she spent her childhood in the now-defunct Republic of Transkei, a nominal state set up by the government as a “homeland” for Xhosa-speaking Black Africans. Though ostensibly offering independence, in reality, these territories were a manifestation of segregationist supremacy. Paradoxically, life in Transkei shielded Bongela from the more visible forms of white hatred and it was only when her family moved to a mixed area in the 1990s that she was awakened to the racialised reality of South Africa.

Bongela’s film is haunted by the disorientation and the guilt that result from this experience of growing up inside an apartheid experiment yet remaining blissfully unaware of its horrors. The non-linearity of this internal contention is beautifully reflected on a visual level; it takes the form of a personal essay accompanied by Bongela’s poetic voiceover, in which a dazzlingly powerful montage weaves in and out of her family archive and historical newsreels. It’s a painful collision of images that shatters the idyllic perception Bongela once had of her own childhood.

In the second half of the film, such contradictions occur aurally. We hear conversations between Bongela and her white friends and collaborators, including the film’s producer, where questions of accountability, microaggression and ancestral guilt float to the surface. These discussions often appear against a dark background, a void that conveys the difficulty of representing past traumas. Painful as it is, the film is also lovingly bookended by the burning of impepho, a ritual of communicating with one’s ancestors. Here is cinema as a form of communion that reaches through time and space.

• Milisuthando is in UK cinemas from 18 October.