Love the novel hope this gives u inspiration to continue even if this is a bit of a slow start it’s still a good fanfic. But if u want NPC recommendations then why not add ppl like Unohana Retsu, Kaguya Otsutsuki, Esdeath or Mirko(MHA) or something like that for the harem. (Not saying u gotta add zanpakutos or dragon slayer magic or even quirks and teigu, especially for Lucian but it would be different and kinda cool but up to you).If u want male characters however, then wy not fun ppl like Natsu&Gray, or even Zoro&Sanji. They are all strong characters (perfect for NPC’s) and have funny interactions and stuff (similar to Albedo and Altear in the Overlord anime). Either way that’s my take and recommendations hope u got enough power stones to keep going and good job my friend I’m enjoying this fanfic so far despite what others might say or think.