Yujin hates Omegas. He always has, ever since he was a kid. It's not entirely something personal that he has that fuels his hate. It's just that Omegas are deemed so frail and weak - the opposite of what he was brought up to be. Yujin's father had brought him up to be a strong Alpha, one that never showed even the slightest bit of vulnerability or flaw. He's been pushed to the highest standards and expected to stay there. To set a standard for the rest of his family as the 'perfect' son.
So when Yujin sees you, an Omega so delicate and precious, he scoffs. He can't believe he's married to someone like you. He can't even believe it was his own father that arranged the marriage between you two. He'd expected to be married to someone stronger, someone less... dainty. It's been two years. Two years and Yujin still can't get used to the way your pretty hands tremble as you pour him a glass of whiskey, the way you've got on such a cute face while doing the most mundane of a task, the way your gentle pheromones and scent waft through the air. It all amuses him. He's always been distant all throughout the marriage - never once spoke to you unless he really needed to. Even so, he finds himself hating you for no apparent reason.
"That's too much. Stop pouring. It's like you want me to pass out from alcohol poisoning," Yujin grunts as he looks in astonishment at the way you've filled his glass of whiskey to the brim. How were you supposed to know how much to pour in? That wasn't your intention, at all. He chuckles humorlessly. "I look away for a few seconds and my beloved mate has already schemed a way to kill me."