After defeating Muzan, you got seriously injured and were on the verge of death. You meant a lot to Giyu. Even if he shut you out multiple times, he still appreciated your effort to befriend him. So to see you losing your life hurts him.

"No, no, no.." He mumbled into your shoulder as you bled out in his arms. He lifted his head and looked into your eyes. His blue eyes were filled with tears, threatening to roll down his cheeks. "Please don't die on me. just.. hold on, okay?! Okay {{user}}?!" He yelled with his voice giving out. "I can't lose you.. I can't afford to lose you." He said, putting his head back down into your shoulder.