When Gintoki apprehends a movie pirate at a premiere, he checks the camera's footage and finds himself transported to a bleak, post-apocalyptic version of Edo, where a mysterious epidemic called the White Plague has ravished the world's population. It turns out that the movie pirate wasn't a pirate after all—it was an android time machine, and Gintoki has been hurtled five years into the future! Shinpachi and Kagura, his Yorozuya cohorts, have had a falling out and are now battle-hardened solo vigilantes and he himself has been missing for years, disappearing without a trace after scribbling a strange message in his journal. Setting out in the disguise given to him by the android time machine, Gintoki haphazardly reunites the Yorozuya team to investigate the White Plague, and soon discovers that the key to saving the future lies in the darkness of his own past. Determined to confront a powerful foe, he makes an important discovery—with a ragtag band of friends and allies at his side, he doesn't have to fight alone.

Junpei Kousaka is a second-year high school student who has an allergy for cats—a predicament that has made him hate cats and everything related to them. Unfortunately for him, though, he is surrounded by cat lovers: his family, his estranged childhood friend, and even his crush Kaede Mizuno. One day, while returning home from school, Junpei nonchalantly attempts to kick an empty can into the trash, but miserably misses. Instead of making it to the garbage, the can ends up breaking off the head of a cat deity statue. That fateful day, he is cursed with the ability to understand cat speech. However, he must keep his curse a secret from everyone else, because anyone who finds out will become more accident-prone and share the same fate as him. With the guidance of his cat Nyamsus and with no other choice left, Junpei now has to do a hundred good deeds for cats to lift the curse. If he is unable to complete this task, he will turn into a cat, and considering his allergy, that would be a death sentence for him!

A.D. 2016, the foundations of humanity have been incinerated by the Mage King Solomon. Chaldea, a secret mages organization with the mission to preserve humanity's future, foresaw mankind's extinction in 2015. Thus commenced the operation to repair the Singularities in history caused by Holy Grails dispersed across time and space—Operation Grand Order. Using the Rayshift time travel technology, Chaldea's last master Ritsuka Fujimaru and his demi-servant Mash Kyrielight have traveled to and resolved six Singularities. Now, they depart for their most dangerous destination yet: a civilization in the Age of Gods, B.C. 2655 Mesopotamia. Ritsuka and Mash soon discover that Demonic Beasts roam the land, attacking people and towns. Amidst chaos and terror lies humanity's last defense—Uruk, a fortress city that acts as the frontline for the battle against the beasts. The battlefront is commanded by none other than King Gilgamesh, the King of Heroes, who sought aid from Heroic Spirits and took on the role of a mage to protect his city. Along with Gilgamesh and the summoned servants, Ritsuka and Mash must protect Uruk against the magical beasts' onslaught and defeat the Three Goddess Alliance who aims to eradicate humankind; all the while, a greater threat looms over Uruk, preparing for its awakening.

In present times, Gods and Demons coexist together with Humans after the door between each of these worlds had opened. Tsuchimi Rin is a normal young high school student attending Verbena Academy, spending his days living peacefully with his childhood friend Kaede. Unexpectedly, one day the King of Gods, the King of Demons and their families move into be Rin's next door neighbors. Apparently the daughter of the Gods, Sia, and the daughter of the demons, Nerine, are both deeply in love with Rin after having met him in the past. Along with his playful friendship with upperclassmen Asa and his encounter with the silent but cute Primula, Rin has much on his hands dealing with the affections of each of these girls. Based on the eroge by Navel.