Black Sun Silver Moon Series by Tomo Maeda

Young and stubborn Taki has been taken under the wing of a new master, a priest who is not your typical servant of God. He pulls Taki into the darker side of life, helping him vanquish zombies and restless spirits by night! Beneath those robes of the Order, hides a dark secret that Taki is determined to uncover even if it means losing his life.

New faces appear in Taki's and Sensei's secluded life that hint at a dark past of Sensei. With an exorcist bent on spearing Taki through and an old acquaintance ceaselessly nudging Taki toward the tempting darkness, the Church is anything but a sanctuary. Meanwhile, the hidden side to Sensei gains more ground with each passing day.

More about Shikimi and Grey's past is revealed as the priest tells them of a bet with some pretty high stakes - his humanity! Taki is more determined than ever to save Shikimi, but when secrets from the half-demon's dark past arise, it seems that Grey may win his bet after all.

Though Shikimi does his best to reassure the villagers, they soon fall prey to worry and madness. With everything he's worked for falling down around him, Shikimi finally turns to his captive for answers. Shikimi, at least, is beyond saving - but what about those he loves?

As Taki finds out about Shikimi's past, secrets of his own family come to light...leading him to actually strike a deal with Grey! How long can Taki keep his pact with Grey a secret from Shikimi, even though it's for the priests' own good?

Shikimi, the half-demon priest was making such good progress, but a fun-filled day in the falling snow turns deadly as his demon half takes over.

Shikimi remains trapped in his own body, tormented by the memories of those he killed. His memories of Taki lend him the strength he needs to survive - but is it enough to overcome the demons when Taki finally fulfils his promise?