Season 1

Will was born in the city of the dead, where he was raised by three undead. Although he was nurtured with love, Will questions his existence in this life-forbidding place where he is the only human alive. He discovers his three parents are secretly hiding something that may explain this mystery, and as if this weren't puzzling enough, he has yet to discover that still more secrets lie within him.

Five years have passed since Will learned Mary's secret, and he is now 13. His undead parents' lessons grow ever more difficult, but Will manages to stick to it. One day, Blood gives him an assignment requiring him to escape from the ruins in the city. Will desperately tries to fight his way out, but an odd sensation of malice stops him. It turns out that malice was coming from an unexpected source.

Turning 15, Will challenges Blood to a fight with real swords as his coming-of-age ceremony, but Gus asks Will to lose on purpose. Will doesn't get a chance to ask Gus about what happened that day in the ruins before he must head into his battle against Blood.

The "God of Undeath" Stagnate's sudden appearance catches the three undead off-guard. Although his attempt to abduct Blood and Mary is interrupted by Gus, the black mist bursting from his chest leaves them no time to feel relieved. Will is unable to do anything as Stagnate says to him with a fearless smile, "It's all thanks to you."

On the verge of death, Will swears an oath to Gracefeel and rises to challenge Stagnate again. However, Stagnate tricks Will into fighting his shadow while he goes off to attack Blood and Mary. When he realizes what's going on, Will rushes back to the Temple and arrives just as Stagnate comes within reach of the two wounded undead.

Will departs from the city of the dead and sets foot in the outside world. After walking in the woods for several days, the first being he meets is Menel, a half-elf hunter. Will is delighted to talk to someone his own age and continues to recall it even after they go their separate ways. That night, he receives a revelation from Gracefeel.

Menel leads Will to a village that's being attacked by monsters. As he banishes them, he learns gravity of the tragedies caused by the attack. Piled-up bodies and burnt houses are everywhere. Then, from their midst, a faint voice catches Menel's attention. The voice belongs to a severely burnt young boy who has turned undead.

Under the guidance of Menell, Will goes to a village that has been attacked by monsters. As he subdues the remnants of the demons, the tragedy of the village gradually becomes apparent. A house burned down by piled up corpses. And it was a boy who was burned by flames and turned into an undead (undead) who called out to Menel with a thin voice.

Will and his friends, who travel with Bee and Tonio, finally arrive at the target "City of White Sails (White Sails)". Will is impressed by the big city he sees for the first time and the people who live there. When healing the tiredness of his travels, the bell of an emergency rings. Looking out in a hurry, a big black shadow crosses over their heads--

Will, who was to have an audience with the lord Ethelwald as a "Killing Wyvern," offers to gather private soldiers to eliminate the frequent damage caused by monsters. Ethel once shows an intimidating attitude to such an outlandish offer, but decides to identify Will and forgive it. Head to a bar where adventurers gather to find friends to fight with.

Will, who was appointed as a paladin, was responsible for the reconstruction of the village and the extermination of demons. One day, he goes to "Beast Woods" with Reistov and Menel, who have two names, "Tsuranuki", in order to search for a unit that does not return. He feels something is wrong with the scattered bodies and proceeds to the valley in the back ...

Will and his friends are addicted to the traps of the demons and have routed. After seeing the seriously injured Menel, Will realizes that he has unknowingly put his companion in a dangerous eye, and realizes the difference in ability between his surroundings and himself. It was Menel who showed anger that stood in front of Will who was going to defeat the demon beast alone.