About the Fist of the North Star Manga Hardcover Volume 15

Among the three Rasho, the generals who rule the land of the Asuras, Hyo hangs on to a little more of his humanity than the others. Deceived into believing that Kenshiro is responsible for the death of his sister, Hyo enters the demon realm to confront him. Meanwhile, Kenshiro searches for Hokuto Shinken's ultimate secret technique, which he will need when he squares off against the demon lord Kaio once again. What fuels Kaio's hatred, and what secret does he hold that could change Kenshiro's fate?