Why did Tomoya Okazaki made his daughter Ushio Okazaki cry in episode 18 of After Story?

Earlier in the episode Tomoya was talking to his grandmother about his father's past. This was when he realized how much his father endured and sacrificed to raise him and in turn he realized how bad of a father he had been to Ushio. He didn't want to repeat those mistakes. So he went to apologize to her and promised to make things right by accepting her as his daughter.

The reason they both went into tears was due to years of emotional repression. This was the first time in five years that Tomoya talked about Nagisa and opened up to someone else, overcoming his own internal struggles. Ushio cried because this was the first true real interaction she had with her father. She hardly knows anything about either of her parents and has been lonely this entire time. So Tomoya finally acknowledging her and asking her to live with him broke open the flood gates.

It wasn't that he was trying to make her cry, it was just an emotional moment for both of them.