Yi Bing doesn't want to, but Shen Sheng is his 'father'. So, he found an empty city in the mortal world. That place was then named the 'City of the Dead'. Huo Ling stayed there. But, not for long since Shen Sheng knew that Huo Ling's soul this time is weaker than him when he was an archangel. Huo Ling will turn into a Soul Fragment again, and has to nurture his soul for him to reappear.
But, Shen Sheng didn't expect that Yi Bing's feelings towards Huo Ling would be so strong. As Shen Sheng watched one archangel (YB) and one grim reaper, he saw that Yi Bing's attitude towards the grim reaper Huo Ling is changing. Shen Sheng guesses that this is both due to their familiarity with each other, sensing each other's soul… and the other is due to Yi Bing's feelings towards Huo Ling. The mind may forget but the heart remembers.