No voices are raised in “ Nagi Notes ,” in the course of a tranquil week or so spent in a remote rural village in western Japan. No seismic incidents disrupt the film’s mellow day-to-day flow, and though we hear sporadic background rumbles from a military base in the area, no urgent mortal threat hangs over proceedings. But the calm is deceptive. Conflict courses through Koji Fukada ‘s subtly stirring new film to increasingly urgent, disquieting effect, raising the human stakes of polite everyday exchanges and encounters: If lives don’t literally hang in the balance, the meaning and quality and value of life does. For two women, and two children, figuring out what they need to be happy, the difference between words said and unsaid is very consequential indeed, whatever the tone of voice. The gentleness of “Nagi Notes” comes as no surprise from Fukada, a humane classicist whose work is marked by hushed restraint even when it trades in larger-scale drama.…