ORV Slay the Princess inspired AU where Kim Dokja appeared in every one of Yoo Joonghyuk's regressions, but they are all just fragments of the Oldest Dream.
The KDJs are never consciously aware of their relation to OD, but they are kind of "preprogramed" to always act differently/take alternate paths in each round, so OD will be able to collect a different story once each KDJ dies and is then reabsorbed.
YJH, the only being (other than OD) to remember past rounds, from firsthand knowledge, slowly makes that connection that KDJ's existence has some kind of relation to his sponsor, OD. This causes him to feel betrayed by KDJ's presence and he proceeds to eliminate him himself in several rounds following this discovery.
But he later realizes that all the KDJs are just as trapped in their roles as fragments of OD as YJH is as OD's incarnation. From this point on, YJH gains a new goal of trying to free KDJ from his fate, as well as completing the scenarios/saving the world.
He can't tell KDJ about this connection (YJH still doesn't know the specifics) because if he does OD just finds a way to snatch up the KDJ of that round up, ending his story prematurely. A circumstance that YJH unfortunately found out through trial and error.
Eventually, YJH realizes that in order to save KDJ he needs to find a way to leave the scenarios behind. KDJ is a human meant to mimic the role of OD (the "reader") while still being able to interact with OD's "protagonist" on an equal level. As long as YJH is still a variable in the scenarios, he and KDJ will always be trapped in their respective roles in this perpetual cycle.
Thus, YJH becomes Secretive Plotter to escape his own role, hopefully spare any future KDJs from their demises, and put himself on a more even playing field with the entity known as OD (who he still doesn't know anything about, other than the fact that they have preexisting connections to both KDJ and himself, as well as being the most powerful constellation in the Star Stream.)