In a world where the night is a slaughterhouse, the ancient Kebaruke monsters stalk the shadows—born from a forbidden alchemical accident. Their only weakness: the very moonlight that guides them turns them into ash.
When an Upper Sun Kebaruke decimates Oolka's village, only she and her brother, Kagroke, survive. But Kagroke is changing. To save his soul, Oolka binds his jaw with a Steel Prayer Seal and joins the Hankure—an elite order hunting King Izan.
Bearing the mysterious Triangle Mark of the legendary first slayer, Yortaka, Oolka must master the forgotten Arts of the blade before the enemy's rotating castle crushes humanity's last hope