After the destruction of their hometown, childhood friends Kafka Hibino and Mina Ashiro make a pact to become officers in the Defense Force—a militarized organization tasked with protecting Japan from colossal monsters known as kaijuu. Decades later, the 32-year-old Kafka has all but given up on his dreams of heroism. Instead, he cleans up the remains of the slaughtered kaijuu after they are defeated by valiant soldiers—including Mina, who has successfully achieved their shared goal. Upon meeting his new coworker, Reno Ichikawa, Kafka faces a mirror of his past self: an ambitious young man whose one desire is to fight as a member of the Defense Force. Unfortunately, the two are soon involved in a freak encounter with a rogue kaijuu. Though Kafka demonstrates his innate heroic nature and rescues Reno from certain doom, he is left gravely injured. While both men recover in a hospital, Kafka is seemingly attacked by another one of the beasts. As a result, he gains the ability to transform into a humanoid kaijuu with the strength and powers of the massive monsters menacing Japan. Dubbed Kaijuu No. 8 by the military, Kafka resolves to use his newfound gifts for the greater good. Tied together by mutual respect, Kafka and Reno set out to join warriors like Mina at the forefront of the Defense Force.

After graduating from a top university with an impressive extracurricular record in the rugby club, Akira Tendou has nailed every step of the way to securing his dream job. On top of that, a beautiful and kind co-worker always brightens his day in the office! Life seems to be going very well for Akira until he slowly realizes that sleepless nights and brutal work are his new reality. Due to three years of mind-numbing labor in an exploitative company, Akira is unable to recognize the tired, unaccomplished person he has become. On track to losing all passion in life like several of his overworked colleagues, Akira finds his saving grace in the most unexpected way possible—the breakout of a zombie apocalypse. With the free time he finally has, Akira decides to complete a bucket list of a hundred things he wants to do before he eventually gets turned into a zombie. Although he is surrounded by the dead, Akira has never felt more alive!

Having a friend that knows you inside out should be a good thing, but in Nishikata's case, the opposite is true. His classmate Takagi loves to tease him on a daily basis, and she uses her extensive knowledge of his behavior to predict exactly how he will react to her teasing, making it nearly impossible for Nishikata to ever make a successful comeback. Despite this, Nishikata vows to someday give Takagi a taste of her own medicine by making her blush out of embarrassment from his teasing.

The famous Seven Mysteries that every school seems to have are a staple of Japanese urban legends. One of the most well-known of these tales is that of Hanako-san: the ghost of a young girl who haunts the school's bathrooms. Kamome Academy has its own version of Hanako-san's legend. Rumors claim that if one successfully manages to summon Hanako-san, she will grant her summoner any wish. Lured by the gossip, many people have tried to call upon her, yet every attempt has failed. However, when Nene Yashiro, a girl hoping for romantic fortune, dares to summon Hanako-san, she discovers that the rumored girl is actually a boy! After a series of unfortunate events involving Yashiro's romantic desires, she is unwillingly entangled in the world of the supernatural, becoming Hanako-kun's assistant. Soon, she finds out about Hanako-kun's lesser-known duty: maintaining the fragile balance between mortals and apparitions.