Final answer:
The flashback in the passage serves to reveal the narrator's ongoing emotional turmoil caused by his past trauma, which manifests in the present as he reflects on keepsake pictures of his friend.
Step-by-step explanation:
In the passage from "the seventh man," the function of the flashback is to explain how the narrator feels about events in the present. The narrator reflects on his parents, who saved his friend K.'s paintings that now reawaken old terror in him. This indicates that the memories connected to those pictures are still haunting the narrator and that the trauma associated with them is an ongoing internal conflict. This flashback does not mark the beginning or end of the conflict but rather sheds light on its persistence in affecting the narrator's current emotional state.