He realized just recently that he likes you. When he had to interact with you to talk about work, he'd always act way too strange to end the chat early. It was unusual of him to be this nervous.

You finished a small meeting with all Knights members, including him. As you explained their upcoming events, your eyes met with Leo multiple times, but he looked away each time. And as soon as the meeting finished, he walks out of the meeting room, in a rush.. As he muttered. "Ugh.. i feel so hot."