The story begins with Ignis, whose skill is "Decoy," being berated by his childhood friend and the chosen Saint, Elma. Elma possesses the "Sword Saint" skill, making her exceptionally talented, while Ignis's skill is seemingly useless, only allowing him to take damage for others. Despite this, Ignis has always protected Elma, a role encouraged by his village and parents who saw him as a shield for their hope. Elma, benefiting from Ignis absorbing all her training injuries, grew powerful and developed a selfish personality, often taking her frustrations out on Ignis, especially when they were alone.
One day, Elma demands Ignis leave her room, stating there's only one room available at the inn. This pushes Ignis to his limit. He declares their partnership over, stating he's useless and she should find a more useful boyfriend. Elma is shocked and protests, claiming she's the one who protected him. Ignis leaves her belongings and departs, feeling liberated. He then checks his status and discovers his skill has evolved into "Immortality," allowing him to instantly recover from any injury, including death. This newfound power is his reason for leaving Elma; he is no longer just a burden.
Two days later, Ignis, now calling himself Ignis, arrives at the port town of Hagey to take on quests. He relishes his freedom from Elma's constant criticism. At the guild, he meets Lisa, a kind receptionist who recommends a quest to collect Lizard Scales. Ignis accepts, confident in his immortality and rapid healing, which also extends to stamina. He heads to the mountainous area where lizards are found. While tracking a lizard, he is suddenly swallowed by a much larger creature, revealed to be a Wyvern, likely due to its nest being nearby. Inside the Wyvern, Ignis uses his dagger to escape, bursting out into the town of Hagey, causing significant damage. He is subsequently dubbed the "Dragon Slayer" and compensated handsomely, allowing him to upgrade his equipment.
A few days later, Ignis leaves Hagey by ship, heading for a volcanic island to relax in its hot springs. He reflects on his peaceful journey, contrasting it with his past experiences with Elma. Upon arrival at the volcanic island of Magrid, he finds the hot springs are closed due to an Adamantea, a giant, tough-shelled turtle-like monster, inhabiting the crater. He overhears a young girl, Tia, who had saved up to bring her mother to the hot springs, lamenting the closure. Feeling a sense of responsibility as the "Dragon Slayer," Ignis promises to deal with the Adamantea. He confronts the creature, which is far larger than the Wyvern. After his new dagger breaks against its shell, Ignis provokes the Adamantea. The creature's enraged headbutt causes a rockslide, revealing a hot spring source. The Adamantea, disliking the hot water, tries to escape, causing the ground to collapse, and it falls into the sea. Ignis is relieved, having fulfilled his promise to Tia.
Back in Magrid, Ignis is celebrated as the "Dragon Slayer." He learns that the Adamantea was a fire god, "Hinokami," and that his skill has evolved again into "Phoenix," granting him immense fire resistance and the ability to transform into a firebird. He is mistaken for Hinokami and becomes the center of a festival. He also meets Kaya, a young shrine maiden and the mayor's granddaughter, who is tasked with serving him. During the festival, Ignis learns that the previous "Hinokami" was a divine messenger, and he is offered the legendary "Phoenix Robe." He accepts, and the robe perfectly fits him.
Meanwhile, Elma, frustrated by Ignis's departure and the inconvenience of managing her own affairs, is determined to find him. She travels to Hagey, seeking the "Dragon Slayer" to recruit him for her party, believing he is the perfect addition to help her surpass Ignis. She learns from Lisa that the Dragon Slayer has gone to the volcanic island of Magrid.
Ignis, wanting to establish his own combat style, travels to the martial arts city of Reolinia. He finds the city in chaos due to the "Martial God Festival," where weapon shops are closed as artisans prepare for the event. He is approached by Fio, a young girl who invites him to her mother Leia's weapon shop. Leia, a strong and pragmatic woman, reveals that her late husband, a renowned blacksmith, was murdered by rivals after winning the Martial God Festival. These rivals are now pressuring her to participate in the festival and threaten to ruin her business. Ignis, moved by their plight and confident in his "Phoenix" skill, offers to win the festival using Leia's weapons, thus protecting them and honoring her husband's legacy.
