Responses

Same here. I remember after done catching up with the novel I found any other BLs were so plain in comparison. It's hard to get the same excitement again after reading Turning.
My only issue about the romance part connected with their past is dragging. After more than 1000 chapters that they finally solved the remaining mysteries of their past relationship. At first I thought that should have been on priority but everything else is executed perfectly!
I don't mind all sub-plots / sub-quests because those are entertaining. Each arc is enjoyable although lengthy.
They are bonded/fater partner. From what I can recall (feel free to tell me I'm wrong) the first time they had sex they unknowingly bonded. It has something to do with Kishiar's power. He can pull and push energy, he can create a bond and severe it. That's why Yuder didn't emit omega scent at all after he spent the night with Kishiar during his first heat. Only Kishiar knew his scent.
When Kishiar "happily" died on Yuder's hands, he severed the bond resulting Yuder's holes in his core/soul and memory. Yuder remember fragments of their relationship but the underlying feelings between them is unknown and questionable. For example whenever they had sex, Yuder in his previous life he thought it was just part of them being alpha and omega, no feelings.
Slowly when his memory returns that he learn that is can not be true.
One thing for sure whenever he remember his past life with Kishiar, it hurts him deeply. At first he thought it must be a regret because he killed Kishiar but the truth is more complex than that.
When Yuder recall his memory from the past, there are traces of Kishiar's feeling too. So although Kishiar severed the bond, the after-effect is everlasting for Yuder until now. He is suffering all alone for so many years not knowing why and how. Some of his questions will get answers in this current life but it's hard to say that his troubled heart from his past completely healed.
To sum it up, what they had is more than just fleeting and ordinary. They both are not ordinary human beings after all.