It's not that he overthinks, but having spent over twenty years living a 'Find Sister' life, his aunt's behavior after finding Chu Xi is absolutely abnormal.
He's not afraid of anything else, just worried that Rong Yan might have the same ulterior motives as Chu Xi, approaching his aunt with an agenda. He only wants to protect his family. To stop the danger before it happens!
Jiang Chenyue glanced at him, picked up her tea again, sipped it gracefully, then put it down, and after a moment of silence, spoke, "…Perhaps it's fate."
"Fate?"
Jiang Chenyue looked at him and said, "In my life, I've never liked someone so much upon seeing them. But from the first moment I saw her, I liked her very much. The more we spent time together, the more I liked her. Even when I saw the hot search on Weibo, my heart skipped a beat."