Khun time travels to the time before he entered the Tower.
Having no recollection of what happened to land him there but not wanting to waste the opportunity he has, he embarks in a dangerous adventure of re-entering the Tower. This time he will climb with Bam and their team mates on his own terms, and he will make sure of it.
"I wish I could've met Bam before you did", Khun now is able to fulfill this wish after travelling back in time, and he sure as hell isn't letting Bam suffer a second time around.
The last words your soulmate says to you are tattooed on your skin. Everyone knew that and prayed they would end up encountering the other half that would mark their skin.
Khun always had known he wasn't a good person, but his soul mark portrayed an even worse future than he could have imagined.
"Even when killing me, you look beautiful, Aguero. "
So he hid his name.