Normally, when someone as mighty as Sword Immortal Qinglian wants to acknowledge someone as his son, he would have done his research. He can't just pick someone up from the street and call them his child.
Here's the issue:
He is a body jumper!
It would be most peculiar if he had a father.
The misunderstanding with Old Devil Yu was understandable. After all, it wasn't just him battling against Old Devil Yu's schemes, but the Fairy Linglong herself, even the remnants of the previous generation's Lady of White Bones.
Two generations of the top-of-the-line joining hands to deceive the currently second-best Old Devil Yu— logically, it made sense.
So, what does Sword Immortal Qinglian mean by this?
The one we intended to deceive is Old Devil Yu, not you.
Why did you have to show up at our doorstep?
There's no way he's actually Old Devil Yu in disguise, is there?
"I don't have a father in this world."
Ji Changsheng and Sword Immortal Qinglian exchanged their hearts honestly.