No Moral Vol. 1 (novel) (No Moral (Novel) #1)
Tehanu

They end up working as partners. But they don't fit. They're like fire and water. Yoonshin doesn't agree with Sehun's ways, and Sehun seems to doubt Yoonshin's competence to get the job done.
But perhaps working together is just what they need to learn more about themselves and overcome each other's differences. And when they do, Sehun finds himself opening up to Yoonshin.