Place it at the end of a confrontation scene, after the blame is laid out, so it lands as the turning point. Before it, use It Was At This Moment He Knew to set up the realization, then let this clip close the scene without another sound after it.
このサウンドについて
This is a roughly six-second spoken line, delivered as a direct accusation: 'You turned her against me.' The delivery carries a sharp sense of betrayal, as if a close bond has been broken by someone else's interference, and the hurt in the voice makes the blame feel personal and immediate.