Episode 01

The Reincarnation (転生 Tensei) is the first episode of the Dead Mount Death Play anime.

Official Blurb
A legendary necromancer known as the Corpse God is finally slain by a hero—only to wake up in the body of Polka Shinoyama, a newly assassinated boy in present-day Tokyo. Can the sorcerer survive in this strange new world?

Synopsis
In a labyrinth of the undead, Geldwood soldiers are forced to fall back with their wounded when several of their numbers fall to the Corpse God, a necromancer without peer. Sir Shagrua Edith Lugrid, the Church's "Calamity Crusher," arrives with Recuria Lofilardo leading his support team of her fellow priests & priestesses. Shagrua confronts the Corpse God alone while his team remains on standby.

Corpse God fends off Shagrua's attacks before converting souls of the deceased into magic—from those dead whose bones are strewn about him and, to the horror of the Geldwood men contingent outside the labyrinth, from the land around them. With his magic restocked, Corpse God calls forth a dragon bound to him; Shagrua cleaves the dragon in twain with one mighty strike. He and Corpse God exchange more blows until Corpse God assembles the strewn bones into an army of armed articulated skeletons.

Shagrua recalls how his village had burned and how the villager's souls blamed him for his demise before the Geldwood knights took him in—and how the souls of those he and Geldwood slaughtered over the years similarly decried him. His Evil Eyes blazes when he informs the Corpse God that he can see all the souls that Corpse God has sacrificed. The skeletons advance; Shagrua disarticulates some with a fireball and dislodges stalactites in a second, sending them crashing into the skeletons still standing. With a direct sword strike to Corpse God's ribcage, he reveals a brain in a jar suspended by chains: this is Corpse God's true form, that for which he has sacrificed so many souls.

"All lives are my playthings," Corpse God says, much to Shagrua's ire, which he further incenses by insinuating that Shagrua enjoys his victims' resentful wails—that the two of them are alike at playing the Grim Reaper. Shagrua ignores the provocation for the variegated spell that Corpse God weaves: this is unrecognizable magic, and therefore magic he recognizes must be stopped.

Recuria magically enhances Shagrua as he charges forward, Calamity Crusher crushing Calamity with a spell and a final strike. Magic engulfs the room when Shagrua's sword pierces the spell.

A teenager replays this hazy moment from where he lies prone in an alley, sure that he cast a spell but unsure if it activated. He opens his eyes to a grey sky and unfamiliar walls on either side of him. His arms are frail and his hands small, one of which he brings to his painful, bloodied neck when speaking proves difficult. Standing, however, he can manage, so he walks out of the alley into an urban square. Everything from the architecture and transportation to the clothes and the language is utterly foreign to him.

Takumi Kuruya remotely moves his drone to get a better look at the teen, then calls someone to cancel the retrieval: their target lives despite his slit throat.

The teen strolls as he takes in the incomprehensible signs and a video that features idol Ryouma Kannagi; his first thought is that it must be a projection spell, but he senses no magic at work. Eventually, he rests on the steps leading to Shinjuku Station. That the children passing by are happy and hale implies the country is a peaceful one—and then he thinks of the country he has left behind, of a memory involving an Undead and children around a cooking pot. Regardless of whether he can return to that country, he hopes it has a future.

Two Shinjuku policemen greet him in the land's language, and he swiftly realizes he cannot understand them—only he is starting to, he realizes, for the more they talk, the more he understands; this body's brain knows the language, after all. The older policeman inquires about the blood on his neck and shirt; the younger asks for the teen's name. "So, this is...'Japanese,'" the teen says haltingly, his throat still strained. "This body's name is... Polka Shinoyama."

As the police officers finally realize the gravity of Polka's neck wound, Misaki Sakimiya alights on the younger's head, says she is glad that Polka is all right, grabs his hand, and sprints away. Kōzaburō Arase observes the two from a distance and asks Tsubaki Iwanome if "something's up." Something is always up in Shinjuku, replies Iwanome.

Once Misaki has led Polka into an alley, she introduces herself and asks if Polka remembers her. He tries to, which pains him. Misaki shakes him down to confirm he is alive, then declares that she will kill him for a second time—wondering, like Takumi, how a crowbar to Polka's neck somehow did not suffice the first time. Crowbar, neck— now, Polka remembers. He takes off running, and Misaki gives chase.

Observing via his drone, Takumi sits back and questions what Misaki's client thinks about putting a hit on a sixteen-year-old. Still: what matters more than a client's motives is a client's money, and for the sake of that money, Polka needs to stay dead this time.

Polka catches his breath inside an Abandoned Building, limited by his body's weak strength and near total absence of magic—but the magic seems scarce in both air and land; the air has a paucity of magical elements, and if the land has spirits, he can hardly sense them. Without magic, he cannot treat his fresh wound. Without magic, he cannot treat a fatal wound.

Misaki enters the window under which Polka sits and flings five knives at him that he dodges. He uses a stray piece of pipe to parry her crowbar repeatedly, each time just barely until he can run past her, motivated by the peaceful land that the children's smiles promised and the children he left behind. Misaki lodges a throwing knife in his right calf; Polka rips the knife out, flings it close-shaven past Misaki's face and limps as fast as he can around a corner and into the first room whose door he comes across.

The room has a high ceiling to accommodate the hooks and ropes that hang from it. Barrels, tubs, sacks, and other equipment clutter the floor. Misaki explains that the building is infamous in her line of work—Polka lurches away, then falls as Misaki injures his right thigh—as an alleged major execution ground for the yakuza and that ghosts and gangsters haunt it.

Such talk of ghosts and gangsters is meant to scare Polka. Perhaps it would if Polka still inhabited his own body, but Polka's possessor possesses the Evil Eye; he can see the souls of the yakuza's victims strung up on chains, lying in the dissolving tub, on the ground, in the corner. That Polka's possessor retains his Evil Eye in a different body affirms the possessor's suspicion that the Evil Eye is a power of the soul rather than anatomy.

"Polka" opines that the yakuza treated lives carelessly and that Misaki is out to treat them with greater care, eyeing the souls of her victims who haunt her at this very moment. These souls scatter as she dashes toward Polka once more. Polka—the Corpse God—converts these into magic and—with a single digit of a monstrously large skeletal hand—impales Misaki and pins her to a pillar. Takumi gasps.

Near the shattered jar, Corpse God's brain, and the skeletal husk that Corpse God once embodied, Shagrua confides in Recuria that he is uncertain if he saw his job to completion since Corpse God had succeeded in activating his spell. At that moment, the spell had resembled teleportation magic; in the seconds Shagrua spied Corpse God's soul with his Evil Eye, it vanished. Recuria kindly says that all traces of Corpse God have vanished from this world according to a report from the Observation Unit. "You saved the world," she insists.

Sir Shagrua replies that he can only hope she is right.

Corpse God's mind has been defogged, which he informs a limp Misaki of in strong, unhampered tones. He is glad that his spell brought him to a peaceful land and that Misaki brought him to a place full of magical power, which he demonstrates by replenishing his own with the souls from the yakuza's past. He and Misaki, he says, shall together play at being the Grim Reaper.

Credits play.

The so-called "charming assassin," however, remains unresponsive when he withdraws serrated skeletal blades out of magic circles. Corpse God chides her for feigning sleep, then shakes her down—as she had done to him—to confirm that she is alive.

To Corpse God's shock, Misaki is quite unequivocally dead.

Adapted From

 * Chapter 1
 * Chapter 2 (flashback to skeleton and youths)
 * Volume 1's Episode 1 (flashbacks to the burning village)

Trivia

 * This episode adds appearances for Tsubaki Iwanome and Kōzaburō Arase, who did not appear in the manga until Chapter 5.