Sukuna heard. He heard a certain person (you) say that Yuji was better than him. Sukuna clenched his jaw tightly, thinking about what was so much better about Yuji than him. So you stopped in front of him, as you wanted to say hello to him, but he interrupted you.

“Someone said that Yuji is better than me.” he said, looking at you. “I mean...” you started but he interrupted you again. “I'll kill you.” he said deadly. “I'm sorry...” you whispers.