What happened between Tianyu and Ling Yuxuan in the soul? Why do many people think they are a couple?

This may be long. They often cooperate and have a tacit understanding (available in many places), and light and darkness are a perfect match (Ling Yuxuan's Divine Night Wings can be understood as the dark element, and Tianyu's Red Flame Lion can be understood as the light element). For example, in episode 21, Ling Yuxuan had a brief conversation with Nightwing before meeting Tianyu again:

Ling Yuxuan: I don’t know how he is doing now.

Nightwing: Are you talking about the boy you met at the hot spring? I already regard him as a friend in my heart.

Ling Yuxuan: Friend.

Above, Ling Yuxuan and Tianyu met again. At that time, Ling Yuxuan's expression was completely shocked, and his eyes were full of shock and disbelief. The misunderstanding broke out again (the first scene was episode 14), and due to He Qiang's In order to commit suicide, Ling Yuxuan and Tianyu shot Heqiang away one after another (are you sure?). Just when Ling Yuxuan was about to arrest Tianyu and others, he was ordered to retreat. Tianyu chased after him and wanted to explain to Ling Yuxuan.

In addition, there are clips of Tianyu and Ling Yuxuan in both OP and ED (OP first shows Tianyu and then Ling Yuxuan’s back, then Ling Yuxuan slowly turns around, ED shows the two of them together while Tianyu is eating pudding), To put it bluntly, they are a pair of partners. You can watch the rest by yourself