Jun Naruse is a chatterbox whose life is colored by fairy tales and happy endings. However, influenced by her deep belief in those tales, she is too naive and trusting, and her words soon shatter her family's bond when she inadvertently reveals her father's affair. Naruse is scarred for life after being blamed for her parent's divorce, and her regrets soon manifest into a fairy egg—a being who seals her mouth from speaking in order to protect everyone's happy ending. Now, even in high school, Naruse's speech remains locked by the fairy egg. Even trying to speak causes her stomach to twist. Though unable to convey her thoughts through words, she is unexpectedly chosen to perform in a musical alongside three other students: Takumi Sakagami, Natsuki Nitou, and Daiki Tasaki. Naruse makes her way to the club room to reject the daunting task, but changes her mind when she overhears Sakagami's beautiful singing. Perhaps the fairy egg curse does not apply to singing, and perhaps Sakagami is the fairy tale prince she has been seeking all along. Will Naruse be able to convey the anthem of her heart?

Half a year has passed. Arriving in the Iron Fortress, Ikoma and Mumei set foot in Unato: another ravaged zone that fell into the grip of the deadly Kabane. In this war-torn zone, the group fends off more dangerous Kabane that are attacking with patterns they had never seen before. The Iron Fortress crew eventually meet up with a survival group which requests their aid in reclaiming the zone. The newly forged alliance ventures deeper into the area of the castle and investigates the peculiar case of these new Kabane. But their search for answers unearths truths that are far more horrifying than they imagined. Forced to confront the reality behind the Kabane, Ikoma, Mumei, and their allies come to realize the despair buried within Unato.

The world is in the midst of the industrial revolution when horrific creatures emerge from a mysterious virus, ripping through the flesh of humans to sate their never-ending appetite. The only way to kill these beings, known as Kabane, is by destroying their steel-coated hearts. However, if bitten by one of these monsters, the victim is doomed to a fate worse than death, as the fallen rise once more to join the ranks of their fellow undead. Only the most fortified of civilizations have survived this turmoil, as is the case with the island of Hinomoto, where mankind has created a massive wall to protect themselves from the endless hordes of Kabane. The only way into these giant fortresses is via heavily-armored trains, which are serviced and built by young men such as Ikoma. Having created a deadly weapon that he believes will easily pierce through the hearts of Kabane, Ikoma eagerly awaits the day when he will be able to fight using his new invention. Little does he know, however, that his chance will come much sooner than he expected...

Ever since her late mother took her to an aquarium when she was young, Tsukimi Kurashita has been obsessed with jellyfish, comparing their flowing tentacles to a princess's white dress. Now living with five other unemployed otaku women, 19-year-old Tsukimi spends her days as a social outcast dreaming of becoming an illustrator. However, her life changes forever when one day, a beautiful woman unexpectedly helps her save a jellyfish in a local pet store. From then on, the stranger—confident, fashionable, and the complete opposite of Tsukimi and her roommates—begins to regularly visit the girls' building. This trendy hipster, though appearing shallow at first, harbors some secrets of her own, starting with the fact that she isn't really a girl at all, but a wealthy male college student named Kuranosuke Koibuchi!