Tsuki no Shirosa wo Shirite Madoromu

Irede: the world's oldest pleasure town, built as an offering to a god. Here alone, myth has endured the passing of millennia. In a townscape dyed vermilion by the light of hanging lanterns, fine wine and masterful music sate the desires of guests who travel from across the continent to experience Irede's wonders—and meet its beautiful courtesans. Yet all is not well here, as shades—supernatural entities born of human desires—lurk in the shadows, their motives known only to themselves, and deep beneath the earth, something primal stirs. When Xixu, a straight-laced military officer, arrives from the capital to become the town's newest shadeslayer, he encounters Sari, a young courtesan with hair the color of moonlight. Thus begins a tale of love and conflict, of desire and blood, and of gods and men.

(Source: J-Novel Club)