yes. The original Shadow monarch was supposed to take over the body during the temple part. He didn't mainly because he was tired, and didn't want to fight anymore so he made the decision to give his powers to sung woo and merge with him. It will get more into this later on during the big sovereign/monarch war the book explains it in more detail so i would recommend that if you really want to fill in the blanks.
Oooh so that’s how it is. I kinda had a hard time grasping on how jin-woo’s ego overcame shadow monarch’s. Haha
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Actually, Ashborn (the original Shadow Monarch) himself mentioned that he had chosen not to erase Jin-Woo's ego and decided to merge with him instead (and basically become part of him), because after all that time spent with him, he found he'd actually become really fond of Jin-Woo and didn't want to lose him (▰˘◡˘▰)
(I always imagine he probably had just as much of a great time watching our boy and cheering him on as us reading Solo Leveling, you know? ╮(￣▽￣)╭)
In the end, when he let Jin-Woo decide if he wanted to be the one to take over, he also explained it ultimately didn't matter all that much who took control, because they'd basically become each other. So, the way I understood it, part of Ashborn would still continue to exist within Jin-Woo thereafter, because they'd become one.
If I understand correctly, Shadow Monarch was supposed to be awakened after the second dungeon raid of Cartenon Temple (absorbing Jin-woo? IDK). Could it be possible that Jin-woo and Shadow Monarch coexist, in a good way?