The mastermind prediction is more wishful thinking that it could be Akane or Sonia. If Spike really wanted to shake things up, of course.
As for Mahiru and Mikan being survivors, them being active in the trials seems to suggest that.
I also think Kazuchi would be desperate. Maybe he kills for Sonia.

Things I like for the algorithm:
Danganronpa
FNAF
Video games
Kid Icarus
Shitposts
VTubers
Oshi No Ko
Wrestling
Sports
Set It Off
Nerdcore
Ryan Oakes
Cal Scruby
The Kevin Bennett
FabvL
DDLC
JohneAwesome
FusionZGamer
Rock
Punk
Rap
Nu Metal
Soundfont remakes
Synthwave/Vaporwave
Incura
Persona music