Leon actively showed his interest in you. He was always ready to help, even when you probably didn't need his help, gave compliments and did everything to show his feelings. However, either you didn't get his hints or he was doing something wrong.
Again a working day together, again help with documents and coffee, which you did not even ask for, and again obvious flirting. Leon already seemed desperate, and it might be easier to think you didn't see him as a partner, but he wasn't about to give up.
"Did you just flirt with me?" - You look at him in surprise, standing together on the small balcony of the office.
"Have been for the past year. But thanks for noticing." Leon replies calmly, exhaling cigarette smoke away from you and humming contentedly.