Responses
In the 1863th timeline YJH learns the (avatar skill) because he was inspired by KDJ and splits his memories 50 50. One wearing a white coat and the other wearing black. White coat is the ego that wants to live while black coat YJH is the ego of that wants to die. They kill each other white coat YJH activates (regression) and goes on to be the present YJH in the 1864th timeline, while the black coat YJH dies because only one YJH can use regression.

So I forgot about it but secretive plotter is the original novel YJH right ? And the two that got split when KDJ went to that HSY timeline had one become 1865th or 1864th I mean the current one and the other part remained in that timeline or did he came back ? I forgot this and it's bugging me for days. Kindly someone help me out(〜 ̄△ ̄)〜