She knows him

Next, Ji-Su showed his respect by first bowing towards the older Director, then towards Ji-Won. As he continued to speak, Ji-Su kept his eyes lowered and acted like a sycophant.

"Rest assured, Senior Director. I will make sure to work hard and pay close attention to my seniors. That way, I will be able to learn a lot from my brother Kang."

"Very good, very good." The Senior Director laughed heartily. 

Clearly content with Ji-Su's rather humble speech, the older man patted the latter's shoulder. At the same time, he turned his head and addressed Ji-Won instead.

"You heard him, Director Kang. Please take good care of young Ji-Su in the future. I want to hear that our Planning Department's two Directors get along as well as brothers."