(Guaranteed complete: the author's previous novel ran for over a million characters.)
Warning: This book is a very, very chaotic crossover mashup of Chainsaw Man, Code Geass, Fate/FGO, Classroom of the Elite, My Teen Romantic Comedy SNAFU, Rascal Does Not Dream, Eminence in Shadow, A Certain Magical Index, Date A Live, The Asterisk War, Chivalry of a Failed Knight, and many other anime (suggestions welcome). It's the author's wildest work, and it has a harem.
This is a bizarre world featuring Devils, Heroic Spirits, Academy City, Shadow Garden, and the Holy Britannian Empire. It's also an outrageous tale of girls trying to conquer the world just to win the affections of the amnesiac Demon King, Jiang Ye / Yukinoshita Ye:
Control Devil Makima / Nayuta: (smiles / points) Thieves should just die~
War Devil Mitaka: Idiots, idiots, a bunch of idiots! You think you can stop me from conquering the world? (hugs Xiao Ye)
Alpha: Is this also part of Lord Shadow's plan?
Scathach / Master: Ah, my disciple really is popular. (summons her magic spear)
Misaka Mikoto: You! (furious / sparks crackle)
Yukinoshita Yukino: My, my, you're as noisy as bugs in the mountains~
Ayanokoji Kiyotaka♀: In that case, a world where only I win and grow will be complete.