As the Fourth Holy Grail War rages on with no clear victor in sight, the remaining Servants and their Masters are called upon by Church supervisor Risei Kotomine, in order to band together and confront an impending threat that could unravel the Grail War and bring about the destruction of Fuyuki City. The uneasy truce soon collapses as Masters demonstrate that they will do anything in their power, no matter how despicable, to win. Seeds of doubt are sown between Kiritsugu Emiya and Saber, his Servant, as their conflicting ideologies on heroism and chivalry clash. Meanwhile, an ominous bond forms between Kirei Kotomine, who still seeks to find his purpose in life, and one of the remaining Servants. As the countdown to the end of the war reaches zero, the cost of winning begins to blur the line between victory and defeat.

Devils cannot take form without a living host. However, if the will of an individual is strong enough, they can overcome the demon and make its power their own, becoming a Devilman. Weak and unassuming, Akira Fudou has always had a bleeding heart. So when his childhood friend Ryou Asuka asks for his help in uncovering devils, Akira accepts without hesitation. However, to Akira's surprise, the place they go to is Sabbath: an immoral party of debauchery and degeneracy. Amidst bloodshed and death, demons possess the partiers, turning their bodies into grotesque monsters, and begin wreaking havoc. In a reckless attempt to save his best friend, Akira unwittingly merges with the devil Amon and becomes a Devilman, gaining the power to defeat the remaining demons. Though it grants him great power, this new partnership awakens an insatiable and primeval part of Akira. Having the body of a devil but the same crybaby heart, Akira works alongside Ryou, destroying those that harm humanity and his loved ones.

Takemichi Hanagaki's second year of middle school was the highest point in his life. He had respect, a gang of friends he could count on, and even a girlfriend. But that was twelve years ago. Today, he's a nobody: a washed-up nonentity made fun of by children and always forced to apologize to his younger boss. A sudden news report on the Tokyo Manji Gang's cruel murder of the only girlfriend he ever had alongside her brother only adds insult to injury. Half a second before a train ends his pitiful life for good, Takemichi flashes back to that same day 12 years ago, when he was still dating Hinata Tachibana. After being forced to relive the very same day that began his downward spiral, Takemichi meets Hinata's younger brother. Without thinking, he admits to his seeming death before flashing back to the past. Takemichi urges him to protect his sister before inexplicably returning to the future. Miraculously, he is not dead. Stranger still, the future has changed. It seems as though Takemichi can alter the flow of time. Given the chance to prevent his ex-girlfriend's tragic death at the hands of the Tokyo Manji Gang, Takemichi decides to fly through time to change the course of the future.

In Tokyo's downtown district of Ikebukuro, amidst many strange rumors and warnings of anonymous gangs and dangerous occupants, one urban legend stands out above the rest—the existence of a headless Black Rider who is said to be seen driving a jet-black motorcycle through the city streets. Mikado Ryuugamine has always longed for the excitement of the city life, and an invitation from a childhood friend convinces him to move to Tokyo. Witnessing the Black Rider on his first day in the city, his wishes already seem to have been granted. But as supernatural events begin to occur, ordinary citizens like himself, along with Ikebukuro's most colorful inhabitants, are mixed up in the commotion breaking out in their city.