Who was the person who took lee muhan away

A Jeoseung Saja, which is roughly the Korean equivalent to a Grim Reaper. They chant the name of the deceased three times and bring them to the underworld.

I thought it was past mc, it wasn't?

How can it be him when mc himself is the reincarnation of his past self? It wouldn't be possible for him to reincarnate if the past mc's soul still existed to wait for lee muhan at that point.