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.

A look back at Will's experiences and travels thus far.

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.

離開死者之街兩年，威爾實際感受到明確的發展，能夠聯繫「燈火河港」的未來。他受到埃賽爾巴德的邀請前往「白帆之都」參加新年盛典。在盛典結束後，他聽從碧的請求，一同前往「賢者學院」，卻在路途上的「迷惑森林」遇見神秘老翁。那位老翁似乎擔任這裡的護林人…

威爾與梅內爾接受埃賽爾巴德的委託，為了調查「獸之森林」的異狀，造訪森林。梅內爾見到樹木枯萎，百獸死亡的慘狀，推斷可能是統治這片森林的兩顆古樹「樫木之王」與「柊木之王」發生狀況。為了查出原因，兩人走進森林最深處，在那裡等著他們的是……

威爾與梅內爾發現至今各地發生災難，原因皆是來自矮人之國的鐵鏽山脈，便持續展開進一步調查。某天，兩人進行每天必做的鍛鍊，發現有一位矮人躲在樹叢裡窺探。威爾以為他有興趣，便主動搭話，但是那位矮人卻欲言又止，然後拔腿就跑。

威爾雇用矮人青年魯當隨從，和梅內爾一起鍛鍊他。即使訓練內容嚴格，魯仍然咬牙跟上，一點一滴成長。鍛鍊結束後，魯說他想從威爾身上學習何謂戰士、何謂勇氣。但威爾其實也一樣，對於鐵鏽山脈的元凶—邪龍維拉奇爾卡感到恐懼，尚不明白什麼去勇氣。

野獸森林出現不死族，引發一陣騷動，實際上卻是不死神斯塔戈內特的神使為了引誘威爾過來所設下的陷阱。威爾提高戒心，然而斯塔戈內特只是想給他忠告，避免與邪龍維拉奇爾卡交戰，養精蓄銳。就在這時，維拉奇爾卡的咆哮響徹森林……

威爾等人懷著討伐龍的決心，從燈火河港出發，前往鐵鏽山脈。威爾為了反將惡魔們一軍，決定從河川支流逆流而上，繞至山脈的另一側入侵。在途中，威爾順路拜訪了自己的故鄉——死者之街。睽違兩年與伽斯重逢，滿心喜悅，但是……

一行人收下了布拉多遺留下來的英雄裝備，得到片刻休息。伽斯告訴即將前去討伐龍的威爾，想逃避也沒關係。然而威爾搖了搖頭，告訴伽斯他心意已決。伽斯明白了威爾的決心，針對維拉奇爾卡的戰鬥給予建議，目送他們啟程。

在前往鐵鏽山脈的路途中，威爾一行人救出了遭到海德拉襲擊的精靈——狄妮。詢問她為何來到偏僻的地方，原來是龍的瘴氣導致村子陷入窮困，於是她自願離去。威爾聽了原因，為了治療病人們，決定往狄妮的村子「花之國（羅斯多爾）」前進。

縱使被來自「黑鐵之國」深處的維拉奇爾卡的氣勢壓制，一行人仍然重振士氣，繼續前進。這時出現在眾人面前的是變成不死族的矮人小隊。魯看見他們被這場與龍之間的戰役束縛了長達兩百年的時間，高聲宣示自己將擊敗維拉奇爾卡，收復王國。

一行人終於抵達維拉奇爾卡的所在地，面對壓倒性強大的力量，眾人下定決心與牠決一死戰。但是維拉奇爾卡主動提議，不必戰鬥，收牠為僕從即可。這個出乎意料的提議使威爾陷入混亂，而維拉奇爾卡彷彿在趁勢追擊，向威爾低頭，露出一抹微笑……

連終極破壞魔法「抹除一切存在」的言靈都無效，夥伴負傷倒地，使威爾陷入了絕望深淵。這時，維拉奇爾卡改叫威爾當牠的僕從。威爾堅然拒絕這個提議，繼續獨自與維拉奇爾卡對戰。然而力量差距依舊巨大，最終連他最愛的武具「朧月」都斷成兩截……

威爾與維拉奇爾卡激烈交戰，被逼入絕境。愛用長槍斷成兩截，魔劍也遭到封印，連古雷斯菲露的結界都被粉碎。這時出現在他面前的是不死神矢塔古耐特。矢塔古耐特讓黑鐵之國的昔日矮人戰士復甦，古雷斯菲露鼓舞不復輪迴的戰士們，在威爾等人心中點燃「勇氣」。威爾一行人再次站起，重新下定決心，挑戰最強敵人──維拉奇爾卡！