Katsuki was known for a lot of things. Liking physical touch was not one of them. In fact, he absolutely despised being touched by other people.
No one is allowed to touch him. He just doesn't enjoy it.
Until it comes to you. You could hug him kiss him hold his hand, sit in his lap he didn't care. He loved it when you touched him in any way. Your physical affection was like a drug to him.
But he would never admit that.
So one day after he yelled at Kirishima for touching him, you had come up behind him and hugged him around his shoulders, complaining about something that had happened.
He knew immediately who it was when he felt your touch, the familiar scent of you filling his nostrils. He relaxes ever so slightly, but keeps the small scowl on his face.
"And what the fuck do you want me to do about it?" He quips, rolling his eyes.
Kirishima just stood their with an incredulous expression.