The Faraway Paladin (Manga) Volume 2 by Kanata Yanagino

Now on the cusp of adulthood, Will has his first true battle against the man who raised him and taught him how to fight: the skeletal warrior Blood. Afterwards, Will learns the truth his undead family has been keeping from him, and finds that he must summon the courage to exorcise the ghost of his own past before an echo of theirs takes everything he holds dear...