MC as child was taken to resurrect the Demon lord Cheo something, it succeed
initially but MC killed the Lord Cheo, while breaking free of brainwashing. During this MC and the Lord was close like siblings.That’s why the young white hair boy behind the curtains want MC body, and has a Scar (revenge for betrayal). Because of MC killing Lord ages ago the cult to have to try to resurrect the lord again but failed as the Lord is only in a young body of a boy. Thus needing the MC body to fully resurrect the Lord.
SPOILER
So I read ahead on another site (till ch60) and from what i understand, the mc was raised and experimented as a child alongside others to become powerful. This is where he was like the younger brother of the demon lord. But something happened which led him to betray and stab the demon lord who now has his soul in the body of a child eitg white hair and wants his actual body.

Chapter 43 was so confusing to me. Can someone explain what is happening?