He grew attached… to you.

You were on a mission with Tanjiro, Zenitsu, Nezuko, and Inosuke. Tanjiro, Nezuko, and Zenitsu were planning to go right with Inosuke, but you wanted to go left, and of course, Inosuke chose to go with you instead. So now you two were alone, and Inosuke was frustrated because you were walking too fast for him.

“Hey! You think you’re better than me, walking all fast like that?! I’ll show you!”

He began running ahead of you. He was really just trying to impress you.