Mairimashita! Iruma-kun - Chapter 359

Assumption: Iruma’s close ancestral family member is Delkira, as to why: Azazel Henry caught a human in the nether realm few hundred years ago and it coincides with the Delkira going missing, and I believe Sullivan and Delkira had a fight when Delkira said “I’m going to quit being a Demon Lord” but Delkira won, KO’d Sullivan, changed his shape, used his soul to create the Ring of Gluttony (also known as ring of Solomon), was intentionally caught by border control and sent to human realm.
Past: Due to Delkira leaving the throne the state of Nether realm started to decay and at some point new 13 crowns where instated (Including Baal), so as to fix the situation Demons started to reinstate the new Demon lord, but failed miserably.
Present: Baal with the help of Naberius Narnia are doing experiments with the human world animals to make unique types of demons, meanwhile Iruma has arrived to Nether realm had gained attention from the school and outside school while just being himself (Achieving Rank “He”).
Future: Iruma at Rank Teth: Baal will drop the bombshell of an announcement of Iruma being a human and turning “everyone” in the Nether Realm against Iruma, and after that is the time skip (Presumably) and Iruma return when the chaos has reached to it’s all time highest.