BL LOVER's manga / #Demons(2)

With rapid developments to the human civilization, the need for God and his angels have decreased at a significant rate. Thus, the angels are experiencing a historic unemployment crisis! With this problem in hand, God decides to start a company that will reduce the unemployment rate in both Heaven and Hell. He hereby founds the company, H&H Roman Company!Original WebtoonOfficial English Translation

Humans keep monsters as slaves for fighting and protection, but there is one, Zai who refuses to fight. Zai is special since he can use magic by creating spells with his songs, but he refuses to sing too... will he, for his master?