The God's War

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?