so I think, that all of this is planned ahead of time. like the one who planed this is the previous demon king himself or maybe just Sullivan"s. maybe they really intended to make iruma to be the demon king for some important world-saving reasons. maybe the demon world needs some touch of humanity? and Sullivans is doing all he can to make iruma the demon king as far as suggesting their grandsons as the candidates. maybe! Sullivan is such a hardcore supporter of the last demon king that he goes as far as searching for the ex-demon king's reincarnated person? and that is iruma kun and the idea of his parents selling him to a demon is " not real". mmh.. idk really..
so yeah that is the planned theory.. and so this is the destined theory.
so if we talk about destiny, it is really not well explain because we can just say everything is destiny. so we will define destiny with the add of a very great reason. maybe the idea of iruma being the destined one is because of the prophecies and hints the author gives us. that's why we are so chillax about him and not really doubting his legitimacy. i too think he is destined because I love him and I am biased, I would destroy the world if he is not the one because he deserved it? idk. not much about destiny because our expectation is as high as the sky. haha
p.s. there wont be any demon king except him. (period)
(I'm gonna SHIFT+CAPS LOCK this, so yeah) OK SO... TH-THEY DON'T HAVE ANY MEDALS!! RANKING MEDALS- I MEAN BADGES!!!! THEY DONT HAVE HAVE IT?! DO YOU NOTICED THAT IRUMA KINDA CHANGE CLOTHES AT THE END AND I NOTICED HE HAVE HIS BADGE ON SO I SCROLL UP AND THEY DONT HAVE ANY!! BUT I THINK THAT ONE BADGE FROM THE FISH GUY IS FROM HIM BEING AN "SUPREME COMMANDER-THING" SO THAT WILL NOT COUNT, IM NOT SURE BUT IM SO HAPPY ABOUT THIS!! ε=ε=(ノ≧∇≦)ノ
there is no main or secondary couple because as it portrays on the cover photo of this story its the four of them so they are, the main characters and I think the author is equally distributing the screen time of each couple because at the start of the story the characters jhian yi and zhan xixi has all the screen time, they were introduce first so now its time for the screen time of the next couple. furthermore, did you forgotten that the first couple had already kissed?! and the development for our tian and mo is probably being shown this time, and its not like the author is neglecting the other couple, right?