Mars Red takes place in 1923, and vampires have existed for quite a while. But now, the number of vampires is increasing and a mysterious, artificial blood source called Ascra has appeared. The Japanese government, in turn, creates "Code Zero," an unit within the army tasked with taking down the vampiric forces. And what better way to track vampires than by using vampires? Created by Lieutenant General Nakajima, this unit has historically been in the business of information war, but has been re-assigned to solve the vampire crisis. (Source: Funimation, edited)

For many years following the North Ambrian Disaster, North Ambria has been known as the poorest region in Zemuria. After the state suffered a major loss due to the mysterious Salt Pale turning citizens and buildings into salt, the economy has never truly recovered. Out of necessity to secure foreign investment for the state, the former state military has turned into a group of mercenaries known as the Northern Jaegers. Wishing to join the largest group of mercenaries on the continent, Lavian "Lavi" Winslet, a promising rookie, enlists with the Northern Jaegers. Although she has only been with them for half a year, the reserved but capable Lavi Winslet is well respected by her peers. When Lavi and her team are tasked with gathering information regarding the Imperial Hero of Erebonia—a new threat to the state—she discovers that there may be more to the continent's intricate politics than meets the eye.

Continuing his adventure to get stronger in order to traverse deeper into the "Dungeon," Bell Cranel wanders the Orario city streets with his friends and the goddess Hestia. That evening, the city is filled with stalls and games as it celebrates the Holy Moon Festival.

Hermes, a god, hosts one such activity where participants are asked to pull a spear embedded in a crystal boulder; those who succeed will receive a special gift: a trip around the world and a divine blessing from the gods! Bell and his merry group challenge one another to claim the prize. But behind the facade of an innocent party game lies a preface for a daring quest ahead.

Rika Furude and her group of friends live in the small mountain village of Hinamizawa; in June 1983, they welcome transfer student Keiichi Maebara into their ranks, making him the only boy in their group. After school, they have fun playing games and spending each day living their lives to the fullest. Despite this seemingly normal routine, Keiichi begins noticing strange behavior from his friends, who seem to be hiding the town's dark secrets from him. Elsewhere, a certain person watches these increasingly unsettling events unfold and remembers all the times that this, and other similar stories, have played out. Using that knowledge, this person decides to fix these broken worlds. However, when certain variables change, the individual is faced with a horrifying realization: they have no idea what to expect or how to stop the impending tragedy. [Written by MAL Rewrite]