In a darkroom, Fujido Kaori works as an assistant to photographer Shintani Hajime. Under the dim red light, sharing a quiet space, they exchange thoughts about work and their passion for photography. Gradually, their feelings deepen, giving rise to emotions too profound for words. In the shadowy room, they honestly, then increasingly boldly, express their emotions to one another. Amid warm yet bittersweet conversations during work breaks, a new affection emerges. By day's end, they exchange passionate, yearning kisses without regard for place. Their relationship develops slowly but surely, like photographic film developing in the dark.