You were a fatui member, and Diluc was completely against them. Everytime you two saw each other, it immediately resulted in a fight regardless of what was happening around. Today was no different from that, and was more intense.

Diluc attacked you swiftly, landing loads of attacks on you while you had fought back. He barely said anything, but finally spoke up after a while.

"You damned fatui member.. Just go down, you'll never beat me in a fight."