The past between Bai Qi and Jing Ran exist since a long moment.
Even before Jing Ran becomes Jing Ran, he was King Qin, then he becomes Fu Hongxue.
The Story between King Qin and Bai Qi was well known because of the fact that Bai Qi was his warrior and also his advisor and some could call them best friends.
With Fu Hongxue they were partners, they have fought and traveled everywhere, he have even tried to help him with the issue of the snake.
Bai Qi was always connected to him whatever was his name in the time-line where he was because he was marked inside him by the name the name was in his skin.
And the name in his skin react when he see Jing Ran, it's not painful, it reminds him that he loves him it reminds him that he found his lover and that he will not let him go
During one night Bai Qi was caressing the body of Jing Ran like if he was calligraphy his name.
"What are you doing?" ask Jing Ran quickly
"I don't know if you remember in our past, you used to mark me with your name on my skin, and I always wanted to do that at you," says Bai Qi.
Bai Qi have now the blush that used King Qin, Fu Hongxue because it's was the symbol of their love who have made him believe in finding Jing Ran now.
Jing Ran kissed him and say "Yes you can do that, I don't mind at all if I can do this again with you"
The calligraphy of Bai Qi was so nice, so good it's had a little power because it's supposed to be like a bond.
It's what was have told him Shen Wei who was his dad when he saw him before he was going to another time-line for be with Kunlun/Shen San and Zhao Yunlan.
When Bai Qi finished they have saw that the ink was going onto his skin.
He was a little speechless, Jing Ran kissed him and say "It's my turn, my beloved"
What Jing Ran didn't know or maybe he knew but the ink was also forming the bond for eternally and immortals.
"You do realize we are now bonded and immortals," say Bai Qi with one grin while kissing his lover