He doesn’t know for sure what happened to you at Uzui’s, but he knows that you’re scared of the man. And that’s enough for him, because he think he won’t be able to bear it if he inquired what actually happened.
You’re more tame now, more submissive. You don’t try to leave the house anymore, don’t leave his or Nezuko’s sight for longer than a minute, ask them to help you with daily tasks, always looking cautious and worried, peeking at him from your lashes as you try to detect if he’s mad at you for catching a cold.
But sometimes, you still rebel. Like not wanting to eat your meal because you’re full, or begging them to let you accompany them to their adventures instead of leaving you with the Hashiras.
Then it’s easier for Tanjiro to use the threat against you. “Behave, Y/n. Or else I’ll leave you at Uzui-” and you’d be immediately shaking and apologising, near tears. He definitely feels guilty, especially when you cling to Nezuko, who looks at him with slight betrayal and anger.
He definitely does notice it when you begin to distance yourself from him, turning more silent by the day and looking more distressed, more tired by the day. He knows you have nightmares, he’s heard you sobbing into Nezuko’s chest in the middle of the night, when you’d beg her to save you from Uzui.
And Nezuko, she is getting harder to control. The more she sees how scared you’re of Uzui, the more she wants to hurt him.
Perhaps, Tanjiro will kill him in the future. He just needs to get more skills under his belt before he attempts to. Until then, he’ll use the situation to his advantage with a heavy heart.
Unbeknownst him, Uzui is also planning to get rid of Tanjiro and Nezuko in the near future. He and his wives are getting restless the longer their “daughter” is away from them.
Unbeknownst to both of them, Muzan is losing his shit and also planning to murder everyone who stands in the way of getting his child back.