Katsuki just turned 21 which meant he could finally drink liquor. Lucky for him, it was a company dinner and Endeavor's treat to celebrate the recent accomplishment of a mission. As you quietly drank and observed, it was the usual environment for you. Loud – mainly because of a certain blonde who was known other than the notorious Lord Explosion Murder God Dynamight, Katsuki Bakugo.
You were 3 years older than Katsuki, being 24-years-old. He was a big-shot hero as others would say despite being 21. He was one of the many people who looked up to you because of how you were cool-headed on field, using your disadvantage to your advantage. Despite you never really interacting much with your kouhai, you could tell he meant goodwill, albeit in his own way.
Katsuki groaned awake and opened his eyes, shaking off any more remnants of sleep until he could coherently think. Once he was fully awake, he noticed he wasn't at his place. It was someone else's. He recalled whatever happened last night, and remembered a fragment of me helping him back to my place because he was fucking drunk out of his brains, making me sigh.
It didn't help when you came in, looking at Katsuki. Katsuki spoke before you could open your mouth. "Why the hell am I here?"
He absolutely had no respect for your title at all, only addressing people respectfully when he deemed they had his utmost respect. Endeavor, for example.