Story

Guts is a lone warrior who was born from a hanged corpse and raised as a mercenary by his abusive adoptive father Gambino. It came to a head when Guts was forced to kill a drunk Gambino in self-defense, fleeing his mercenary group and becoming a wandering sellsword. His fearsome reputation catches the attention of Griffith, the charismatic leader of a mercenary group known as the Band of the Hawk. Griffith forces Guts to join the group after defeating him in battle, with Guts becoming his best fighter and main confidante. The Band is hired by the kingdom of Midland to help in its century-long war against the Chuder Empire. Guts learns of Griffith's desire to rule a kingdom of his own and his mysterious pendant known as a Behelit. The Behelit is instrumental when they are spared by Nosferatu Zodd, a monstrous immortal who leaves Guts with a cryptic warning of a painful demise for being Griffith's friend.

As Griffith mingles with Midland nobility while acquainting himself with the king's daughter Charlotte, Guts begins developing feelings for his fellow commander Casca, the Hawks' only female member. Upon overhearing Griffith confessing to Charlotte that he only considers someone with their own dream as a friend, Guts decides to leave the group once Midland has won its war so he can find his own dream. Guts' decision inadvertently causes Griffith to fall into an emotional spiral that culminates in his arrest for seducing Charlotte in a moment of weakness. He loses his Behelit while subjected to endless torture, and the Hawks are declared criminals by the Midland army. Guts, having spent a year training to become a better swordsman, is warned by a mysterious being known as the "Skull Knight" that his actions have instigated an "Eclipse". Learning of the Hawks' predicament, Guts rejoins them to rescue Griffith, while also consummating his feelings for Casca.

Despite a successful rescue while fleeing to Midland's borders, the Hawks learn Griffith became physically incapable to lead them as they, Casca, and Guts determine how to proceed. When Griffith regains his Behelit while injuring himself during a solar eclipse, the pendant uses his blood to establish a temporary convergence of the physical world and the supernatural astral realm in the form of a hellscape. The Hawks encounter a quartet of archdemons known as the "Godhand" who have gathered for a ritual known as the Eclipse, revealing that Griffith has been chosen to become their final member and can only transcend his humanity if he offers his comrades as sacrificial offerings. Griffith accepts once reminded of the person he has always been. The Hawks are branded with demonic sigils, marking them for sacrifice and are subsequently slaughtered by the Godhand's Apostles—humans like Zodd who attained power by sacrificing their loved ones and humanity. Only Guts and Casca survive the massacre, but Griffith's first act as the being Femto is to rape Casca in front of Guts, with an enraged Guts losing his left forearm and right eye in his attempt to save her. They are rescued by the Skull Knight, but the ordeal traumatizes Casca enough to regress her mind to a childlike state. Guts learns from the Skull Knight that their "Brands of Sacrifice" makes them targets for specters and other beings of darkness on a nightly basis. Guts leaves Casca in the care of the blacksmith Godo, his adoptive daughter Erica, and Rickert, the last and youngest member of the Band of the Hawk, who survived by not being present at the Eclipse. Godo outfits Guts with a giant new sword, "Dragonslayer", and a prosthetic left arm with a built-in cannon and crossbow. Guts begins hunting down the Apostles to find and kill Griffith while followed by a demonic phantom called the Demon Child, which is actually Guts' and Casca's unborn child deformed by Femto's rape.

Two years later, after having killed many Apostles and earning the nickname of "the Black Swordsman", Guts is joined by an elf named Puck. They are captured by Farnese, captain of the Holy See Church's Holy Iron Chain Knights, who believes Guts is a foretold harbinger of the apocalypse. Guts escapes after saving Farnese from specters, returning to an ailing Godo while learning that Casca wandered off. His search for her takes him to the refugee-infested city of St. Albion, a city the Godhand have prepared as the site for an Incarnation ceremony to give one of their own a physical form. Guts saves Casca from the fanatical Holy See bishop Mozgus as the city descends into nightmarish chaos from the souls of the dead attacking. Joined by Farnese, her bodyguard Serpico, and a young thief named Isidro, Guts and Casca survive the ordeal as a misshapen apostle living under St. Albion ingests the dying Demon Child and uses its body to reconstitute Griffith into a physical form.

Guts encounters Griffith and Zodd at Godo's home and they engage in battle; the nearby enchanted mine, which sheltered Casca from the nightly demon attacks, is destroyed by Zodd while Griffith realizes some lingering traces of the Demon Child persist within him. To try and find a means of restoring her mind, Guts decides to journey with Casca to Puck's homeland of Elfhelm, on the island of Skellig. He allows Isidro, Farnese and Serpico to follow him out of fear that he will lose control of himself to his dark impulses—embodied as a demonic black dog within his mind—with Farnese becoming Casca's primary caretaker. At the same time, Griffith creates a second Band of the Hawk with Zodd and other Apostles to save Midland from the invading Kushan Empire, led by their rogue Apostle emperor, Ganishka.

Guts' group encounters the witch Flora and her apprentice Schierke while saving a village from marauding trolls. Schierke begins to teach Farnese magic and dampens the effects of the sacrificial brands on Guts and Casca via magical seals. Flora gives Guts a dangerous relic known as the Berserker Armor, which increases his physical capability with the added risk of being consumed by his inner darkness. Flora is later killed when the New Band of the Hawk destroy the tree she made her home in. After escaping the destruction of Flora's home, during a full moon, Guts' party encounters Moonlight Boy, a small boy who does not speak but expresses a fondness for Guts and Casca. The boy disappears after the full moon passes. While Guts and his party secure a ship called the Seahorse, captained by Farnese's erstwhile fiancée, Prince Roderick, to reach Elfhelm amidst a Kushan attack on the port, Griffith's war with Ganishka reaches its climax; the emperor is destroyed following his transition into a god-like abomination that causes a worldwide overlapping of the mortal and astral realms. Unopposed and with Charlotte and the Holy See's blessing, Griffith establishes the city of Falconia to provide refuge for Midlanders and the rest of humanity from the numerous mythical creatures that manifested when the realms merged.

After a dramatic battle with a supernatural island-sized monster known as the Sea God and recruiting a merrow girl named Isma, Guts' party reaches Elfhelm. The elf ruler, Danann, helps Farnese and Schierke travel into Casca's mind and restore her to her former self. Despite her recovery, Casca is still traumatized from her ordeal to the point of finding it difficult to be around Guts without remembering the events of the Eclipse. Farnese and Schierke begin training with the other apprentice witches and wizards living on Skellig, the former taking an interest in the power to heal human souls to help Casca. At the same time, the Skull Knight tells Guts his journey is at an end, introduces him to the creator of the Berserker Armor, and explains his own past with the Godhand and its leader Void. The Moonlight Boy appears on Elfheim during a full moon. Danann senses no malice from the child and he is allowed to stay, forming a mother-son bond with Casca. It is revealed that Moonlight Boy is the Demon Child, who can take control of the body Griffith resides in during a full moon. Griffith regains control of his host when day breaks and unnerves Guts with his inability to harm him before Zodd arrives. Griffith proceeds to abduct an incapacitated Casca while killing the island's giant spirit tree. The tree's destruction not only unleashes a torrent of evil spirits that nearly submerge the island, but also cause Danann, Isma and the other magical creatures, except Puck and Ivalera, to disappear into the Astral Realm. The survivors sail off on the Seahorse, defeated with their only advantage against Griffith gone. Guts breaks down in despair as a whirlpool begins to draw in the ship. Meanwhile, Griffith and Zodd return to the mainland with Casca.