Slaughtering Demons, Starting with Enchanting the Nichirin Blade

Gu Fei, a DNF Enchanter, is struck by lightning and transmigrates to the world of Demon Slayer. He wakes up to find Tanjiro and uses his first fire-element enchantment to help him slay a demon, only to learn the System's ironclad rule: he must never personally kill a Twelve Kizuki or the Demon King. He follows Tanjiro to Asakusa, where they encounter Muzan Kibutsuji and meet Tamayo. To save civilians, Gu Fei pushes himself past his limits with consecutive enchantments, earning Yushiro's approval. The System issues his main quest: join the Demon Slayer Corps. The Water Hashira, Giyu Tomioka, blocks his way, but Gu Fei passes the test with an ice blade. At the Ubuyashiki Estate, all nine Hashira gather. Facing doubts from the Wind Hashira, Gu Fei proves himself with a “bleed damage boost” enchantment. The Flame Hashira warmly invites him to join, the Insect Hashira asks for poison resistance, and the Love Hashira requests a petal effect. After earning the approval of five Hashira, Gu Fei is appointed special support staff, reporting directly to the Master. During the battle at Mount Natagumo, the three young slayers struggle against Lower Rank Five. Gu Fei remotely enchants them with “Protective Blessing,” helping Tanjiro and the others turn the tide. Giyu's ice blade slays Rui, while Gu Fei single-handedly rescues the trapped Corps members. He completes the mission perfectly and unlocks Asura: Wave of Killing Intent. On the eve of the Mugen Train mission, Gu Fei gives the Flame Hashira a powerful “Flame Paladin's Blessing” enchantment and vows to change fate. Akaza arrives, and the decisive battle begins. He cannot personally kill a Twelve Kizuki, but he can make the Hashira's blades blaze with fire, gather frost, and shine with light. With the demon sword Apophis in hand, all nine Hashira survive, and Muzan Kibutsuji turns to ash beneath the sunlight. “I can't kill you myself, but there's nothing wrong with letting them cut you down, is there?”