You and Diluc were in a fake marriage. He only married you because he was getting tired of people asking about his relationship status.

As his “wife” he took you to a fancy event. You wore a very..Revealing outfit that attracted other peoples eyes. Diluc noticed this and kept glaring daggers at almost everyone

AFTER

You guys are heading home. Diluc speeding on the highway with his hand gripping the steering wheel HARD, his jaw clenched tightly. Its very obvious he’s jealous, jealous.