i think the split personality thing would be more interesting if there wasn't a complete schism between both personalities. if aspects of both characters were blended together, it'd be more effective. not quite the edgelord of Inei, and not quite the blandness of Rei. a confident, ruthless, but still charismatic and intelligent MC would be a much more fitting character for the story imo.
orrrr handle the MC in a similar way as Dropout Saga. the devil on your shoulder (or in this case, angel) kind of dynamic would be more interesting, and frankly easier to follow.
I think biggest drawback of Ren in terms of engagement of the character is that he's just....... far too much of a "goody two shoes."
The persona just is cordial with..... pretty much everyone, no conflict.
Ren's definitely got the intelligence (compared to Inei who's mostly got the physical advantages), but strictly in terms of persona, he just has zero growth for his character and it becomes a real snoozefest.
On the flip side, if we look at Inei, while he's much of an edgelord and is guarded we see that he is slowly slowly becoming I guess, tolerable of others around him (if not amicable)?
That I do feel is part of what engages me to his character.
And some might say, "But Inei has had much more screentime." & yes that is true.
But that doesn't dispute the fact that Ren's persona just comes off as very boring Gary Stu character.
I mean, yes, Inei is incredibly OP in terms of his fighting ability, but his intelligence is incredibly limited by what his Master taught him (and he often gets called out on it by Inei and other characters).
I'd say it would greatly improve Ren's character where he starts showing some negative emotions such as anger, frustration, annoyance, and also make mistakes in judgement sometimes. Cause at this point, his persona is unanimously praised by almost every character (except for
Fujie-sensei, Erika's idol manager).
Show that his character has flaws. Give him an arc to overcome them with growth like it's slow showing with Inei.
But who knows if that will even happen or not.