Kloff does not remember his past life in this universe because he is not the same Kloff from season 1, this is another Kloff, a variant from another universe that is calmer and less psychopath than his other self from the first universe.
This Kloff apparently has visions in the form of dreams of what his other self or variant from the first universe did to Aeroc and feels disgusted every time he has them, because of these dreams Kloff from this universe fears hurting Aeroc
On the other hand, the Kloff from the first universe also reincarnates in another universe and has his memories from the first universe, there he meets the variants of Aeroc and Rapiel but is rejected by both, since both boys consider him a dangerous and crazy person.
Idk about anyone else and don't hate me but I despise the fact that Kloff doesn't remember shit. I mean it's not like Aerok was a decent person in the first timeline but it just doesn't justify kloff doing him wrong and giving me some big ass trauma. I've never been emotionally challenged to this extinct- hell was i ever damaged to a degree from which i couldn't make a recovery. But while reading this I could feel every bit of what was happening as if it was me in there. My point is i get so pissed whenever Aerok flinches because clueless and innocent Kloff gets close to him and so do I