The Night Empyrean, Ye Qianyu's father, was actually Barbarian Emperor's master. That's why he was so close to Ye Qianyu. As an emperor, he was actually willing to carry the sedan for her and she even called him "A`mun." So the two of them can be considered one family.
But the Barbarian Emperor was fond of Ye Qianyu in the romantic sense. Yet, Ye Qianyu had no such thoughts and clearly told her so and that he should instead focus on cultivation.
He was the one who fought with Qin Wentian at the mine. He was extremely unhappy with Qin Wentian after he joined the Thousand Feathers Palace. Especially because Ye Qianyu was always helping and trying to be close to Qin Wentian. She directly rejected his advances right in front of his face. Yet, Ye Qianyu still told Qin Wentian to stay in her palace. That made the Barbarian Emperor hate Qin Wentian even more.
He will leak Qin Wentian's identity as a bandit to the Jialan Monarch. However, the Barbarian Emperor only had a single intention. He wanted Qin Wentian to die. He naturally didn't wish for Ye Qianyu to be implicated within. Although Ye Qianyu's treatment towards him was far inferior compared to Qin Wentian, he was still in love with her and has been so for many years. He only wanted Qin Wentian's death.
The Jialan Monarch will use a strategy by spreading that they will execute Beiming Youhuang in one month to force him to show himself. But that was just a lie, Beiming Youhuang was just in a secret realm and couldn't be contacted. Having no news of her, Qin Wentian will come to save her and fall in the trap. Ye Qianyu will appear save Qin Wentian but will be captured instead, the whole Thousand Feathers Palace will also be captured and the Barbarian Emperor will betray the sect to side with the Lifire Palace. Qin Wentian will kill him for it not long after.