Second part of Dungeon ni Deai wo Motomeru no wa Machigatteiru Darou ka IV.

The students return as school is back in session for the second semester. Following their exploits on the island during summer vacation, Class 3-E continues to sharpen their blades with their sights set on their teacher, the slippery Koro-sensei. They have more to worry about than just their teacher, however, as enemy assassins, both old and new, are out for the increased bounty on the octopus' head. Moreover, their rivals in Class A, as well as Kunugigaoka Junior High's fearsome principal, stand to block Class E from achieving academic excellence. With all of these obstacles opposing them, the group must continue to work together in order to overcome their foes and accomplish their goal of successfully assassinating their teacher. [Written by MAL Rewrite]

For hearing-impaired university student Yuki Itose, silence has been a natural part of life since birth. Her world is small and isolated; she commutes to campus, interacts with her best friend Rin Fujishiro, and communicates through writing and text messages—a lifestyle that offers little to no change. One day, during her commute, Yuki meets fellow student Itsuomi Nagi, a multilingual travel enthusiast and friend of Rin. When Itsuomi learns of Yuki's condition, he takes it in stride, moving Yuki's heart. From this one simple gesture, Yuki and Itsuomi's lives start changing day by day as they let each other into their own worlds.

Following their heroic efforts at Walter Park, the students of the misfit class return to Babyls Demon School after their summer vacation. What awaits them is not only adoration and admiration but also the shocking revelation that, in order to stay in the luxurious Royal One classroom, the entire class must be promoted to Dalet rank before entering the second year. As the Harvest and Music Festivals are right around the corner, there seem to be ample opportunities to rank up. Doing so will not be simple, however, as no class thus far has managed to accomplish such a feat. Hoping to give the misfit class a chance to achieve the improbable, the school appoints special tutors to aid in confronting the challenges that lie ahead. With his sights set beyond Dalet, Iruma Suzuki decides to take strides toward the goal of ranking up, starting with gaining acknowledgement from his special tutor: the short-tempered and selfish Bachiko Barbatos.