Yujin looked at Yitian leaving wide-eyed. Atlas felt just as stunned. He knows from the previous twins how much they need to share everything and always be around the other so it's shocking that Yitian is willing to walk away and even gave them his blessing.
He checked Versem and saw that the twins were indeed planning to come back after the time frame. When they left he never checked on them because he didn't want to see them being all lovey-dovey with Yan.
He knows it's been hard on Yitian only because of the OGTL but it seems like it's worst than he thought. Yitian stopped when Atlas asked:
"Can you?"
Yitian turned around.
"What?"
"You said that Yujin can't be without me. Can you?"
Yitian swallowed and looked down. Of course, he can't be without him but he doesn't want Yujin to be unhappy when this is all his fault. He's the one who compared him to Yan and made that comment when he came back.
Love's Alchemy: Breaking Shadows