Code Vein - Wikipedia

Setting

Code Vein is set in a post-apocalyptic near future containing the Revenants: undead humans with vampiric abilities and strength who can only die by destroying their heart, and require human blood to stop from entering a frenzy and mutating into the Lost - uncontrollable cannibals devoid of reason.

Participating in an experiment to stabilize the Revenant population and stave off the Lost, a girl named Cruz Silva volunteers to become the "Queen of the Revenants", though she later frenzies herself and goes on a murderous rampage. More Revenants are created to defeat the Queen in a mission dubbed Operation Queenslayer, led by Cruz's father Gregorio Silva.

Though they killed Cruz, the Lost remain, and the Bloodsprings (plants producing Blood Beads as an alternative to human blood) begin to dry up. Silva establishes a provisional government shortly after Operation Queenslayer, and the levy on Blood Beads that this government establishes worsens the shortage, leaving many Revenants to turn into the Lost.

Story

The protagonist awakens within the ruined city of Gaol of the Mists, where they[b] meet Io and Louis Amamiya. They make contact with the vestige of a Lost without becoming frenzied, acquiring its memories and Blood Code, a unique property that grants Revenants their powers. Louis learns that the protagonist can use the Blood Code of whoever shares their blood. The group search for the source of the Blood Beads to remedy the scarcity. They meet Mia Karnstein and her near-frenzy brother Nicola, who is seemingly killed by a mysterious hunter. The protagonist later regains some of their memory, revealing their role in Operation Queenslayer alongside Silva and the hunter Jack Rutherford. The protagonist permanently killed the Queen, but was exposed to her blood and near-frenzy. Jack was forced and failed to kill the protagonist.

The group encounters a massive Lost, the Successor to the Ribcage, which the protagonist absorbs. They learn that the experiment that made Cruz into the Queen rendered her immortal. Silva decided to divide Cruz's body into pieces called 'Relics', each placed in a voluntary Revenant, becoming Successors who sealed themselves in crypts while resisting the Relics' corruption. The group finds Louis' sister Karen, a Successor. The protagonist learns that they became a Successor by defeating Cruz, and plans to soothe other Successors to prevent the Queen's resurrection. Jack is revealed to be a Successor and caretaker of the other Successors alongside his companion Eva Roux.

The group travels to the mountains and faces the real Nicola, revealing that the one who accompanied Mia was a clone that Jack killed as its existence hastened Nicola's frenzy. The group reaches and soothe Nicola as he was fighting the Relic's influence, reuniting with Mia. Jack is assaulted on the way up the mountain by Juzo Mido, a scientist who believes Revenants are the next step in evolution and is seeking Silva, now a Successor. Jack reveals that the Gaol of the Mists was created by Silva to contain the Revenants for the sake of humanity and needed constant blood to maintain which led to the Blood Bead levy system. Jack joins the group to secure more Relics, including Eva, a new Successor who joins the group after being restored.

They confront Mido, who reveals his plan of undoing the Gaol as he kills his men so the Relics in his possession merge into Silva, causing him to mutate into the frenzied Skull King with the Gaol briefly dropping enough to reveal the outside world is filled with monsters. Upset at Silva resisting the Relic, Mido explains though the Gaol started off as a prison for Revenants, it has become a shield from the monsters outside as he desires for Revenants to fight the horrors and evolve. The group defeats him before he can reach Silva, but the damage is done and the group's only option is the protagonist resolving to replace Silva as the Successor. The group make their way to Silva's crypt and learn Io is a clone of Cruz, one of many sisters acting on Cruz's desire to prevent her resurrection by attending to the Successors. The group battle the Skull King, who loses control of his Relic as it calls the other Relics who transform him into the newest Queen, the Virgin Reborn, before being defeated.

The ending depends on how many Successors the protagonist saved. If none are saved, the protagonist is killed by Louis when they begin to frenzy while attempting to absorb the Relics with the protagonist's surviving companions becoming the current Successors. If the protagonist only saves some Successors, they absorb Silva's Relic and take his place in maintaining the Gaol, with Io staying by their side. By saving every Successor, Io intervenes and takes the protagonist's place, absorbing all Relics. With the Successors restored, Io transforms into a new Bloodspring, the Weeping Tree, replenishing the Blood Beads and maintaining the Gaol as the city begins anew. Io produces a Blood Bead carrying her memory, allowing the protagonist and the group to venture to the outside world to save others, alongside their comrades almost a decade later.