Angels Nathaniel and Chasen were fated twin flames that burned for each other but for 1000 years Nathaniel had denied it choosing to be alone and in turn forcing the same on Chasen. 
When they are both sent on assignment to earth as married humans to save a child Chasen hopes everything will change but Nathaniel is still in denial.
Nathaniel is the epitome of grumpy i laughed at some of the hints he complained about especially when Chasen tells him about Chai tea and he rants on about chai means tea so why would anyone in their right mind call it tea tea .