Continuing their perilous descent down the Abyss, Riko, Regu, and newfound friend Nanachi reach the Abyss' fifth layer, The Sea of Corpses. Upon arriving at the research station known as Idofront, the main trio encounter the mysterious Prushka, the alleged daughter of Bondrewd, who leads them to the White Whistle responsible for Nanachi's dark past. Despite the welcoming appearances of Idofront's residents, Nanachi warns the young adventurers that things are not always what they seem. With the only route to the sixth layer shrouded in mystery and Bonedrewd's schemes awaiting them, what sacrifices must be made in order to continue the journey down to the bottom of the Abyss? [Written by MAL Rewrite]

Akane Nishimura's quiet nature makes her classmates perceive her as a gloomy and unlikeable person. Combined with her intimidating gaze, it earns Akane the ominous nickname "Grim Reaper," condemning her to endless bullying for her supposed cursed powers that bring misfortune to everyone around her. However, none of these rumors deter transfer student Taiyou Takada from trying to befriend Akane. As someone who finds the supernatural fascinating, Taiyou approaches the Grim Reaper without hesitation, blissfully unaware of the complicated situation within the class. His bright personality and optimistic worldview may just bring about the change that Akane desperately needs.

The Walpurgis Royal Academy of Machinart was founded alongside the development of "Machinart," machine magic capable of giving life and intelligence to mechanical dolls subsequently called as "automaton." Its aim: train skilled puppeteers to control the automatons, as militaries across the globe have begun incorporating Machinart into their armies. After miserably failing the academy's entrance exams, Raishin Akabane and his humanoid automaton Yaya must defeat one of the top one hundred students to earn the right to take part in the Evening Party, a fight for supremacy between puppeteers using their automatons. The last one standing is bestowed the title of "Wiseman" and granted access to the powerful forbidden arts. Thus, Raishin challenges Charlotte Belew and her automaton Sigmund to a duel, but before they even begin, Sigmund is attacked by other students. After saving his opponents from their assaulters, Raishin cancels the duel but is forced to search for a new way to gain access to the Party. Driven by the tragedies of his past, Raishin fights alongside Yaya to rise to the top and claim the title of Wiseman. [Written by MAL Rewrite]