From Tokyopop:
In the frontier of the American West, a veil of evil threatens to engulf humanity. Servants of the fallen archangel Temozarela are paving the way for their dark lord's resurrection. One man stands in the way of the apocalypse: Ivan Isaacs, a fallen priest who sold his soul to the devil Belial for the power to fight evil. Armed with a wicked blade and silver bullets, Ivan will give the heretics a baptism of blood in his pilgrimage for humanity's redemption.

From ilovemanhwa.com:
BLOCKBUSTER SCI-FI CHI ACTION FROM THE AUTHOR OF PRIEST! Ton-up kids�� craziest leader Chiwoo prepared a big gang fight to celebrate his 17th birthday, but he finds his father prepared a bigger party as he promised when he left Chiwoo 10 years ago. The party starts with a sudden visit of the agents from the Central Incantation Center of Korea and its enemy, the Unions. Chiwoo is simply shocked by their spectacular Incantation War, but does not realize his power, the Mighty Spirit, the ultimate power these two countries would risk the war for. Which way will this birthday present lead Chiwoo to?