Xu Shaoyan is a hidden character. I suggest that you save your progress when you encounter certain choices. If the affection doesn't increase, you can reload and try a different option.
Viewing post in Idle Clouds Drifting Among Mortals comments
I did that the first time and gave up on the fourth try. I re-did that today to follow your advice and I can't get the path. I even took notes on points (10 pts Ask; 5 pts Knife; 5 pts Act; 5 pts Return; 5 pts Return Courtesy so it's actually 30 points and not 20 like I thought but still far from the 55 points needed.) I even tried without giving points to any other RO. I don't seem to see his route even though his name appears at the branch point.