Thanks for reminding me about this.
I think they should have plot manipulation and possibly acausality type 5 for the following reasons:
1) There's an ability that was created by the second demon when she gained full control of the system. It's called Karma, and it was used to teach students a lesson because heroes didn't care if they died due to the concept of regression. Every time they died, it would affect their story, resulting in harsher conditions at the start of their adventure and less support and appreciation from the summoner country and its population. For example, items would be sold at a higher cost, and it would be harder to convince people of something after each regression. They would not receive any help on missions, and the route to obtain their holy sword and defeat the demon king would become much harder...
2) It was used to control the way some of the characters act, for example, the demon king's fragments. his fragments talk to the hero like an RPG game and keep repeating the same script in every dimension, even though the demon king is fully conscious of everything and can control any fragments, When heroes ask the demon king questions that are out of the script, like, for example, 'who is behind all of this,' he will never respond to their questions and will continue saying the same thing (because he was sealed). It was stated once the characters who reach the transcendental realm (Z rank) can break free of the system rules. So maybe that's why they give the heroes the debuff perk and let them repeat everything from the beginning, including their stats (Han Soo was the first one to reach Z rank because of the black box, which also let him ignore the system rules and keep his power after regressing). The debuff perks equal the demon king's power to the heroes. Perhaps that's also why the demon king kept telling the heroes to try and grow stronger because if the hero got a Z skill, the demon king would get Z too. That's why, in the sixth playthrough saga, for the first time, the demon king acted differently and left the tower (he was sealed there). It was stated in one of the chapters that if the hero grew stronger, he might break free from the dimension and run away from the world. And that is the demon king's plan, and he succeeded but in another way by tricking Han in the same arc and letting his daughter, the second demon, meet Han Soo, which means the second curse will affect him and change fate, so Han Soo will become the second demon and free himself from the dimension. So yeah, Correct me if wrong I think that's plot manipulation and possibly acausality type 5 for characters with Z rank. And sorry for my bad explanation : )