Basically after the events of Basics and Behavior things went back to normal for most people except Engel with most of his friends dead he isn't in the best mood or head space he starts to isolate himself from others but that doesn't stop the bully trio from Bullying the hell out of him.

Eventually one day he is just laying down in the grass behind the school when something appears and enlightens him and eventually then it gives him a goal that there is more to this world you just have to seek it

So the next day Engel Walks to ∆lice's room Heads inside while word gets around he went to her room and most think he went in on purpose to die and Oliver is just like "Well hope My GF likes Birds" but turns out thanks to the entity that spoke to Engel he is able to actually overpower ∆lice and Kills her and absorbs her but then at that moment a million different thoughts fill his head and he sees beyond the stars he sees different universes and people and then thanks to ∆lice's DNA entering his body he changes to look like how he looks now

Then he bursts out the room Bloody ink dripping off him everyone is Flabbergasted and to top it all off he holds up ∆lice's pendent symbol thing and breaks it and thus a calamity falls

2 weeks pass

Most people are separated now in small groups while some are Dead and Oliver alone now wants to go face Engel now dubed by many Endgel as they face each other