Heroic Spirit Transformation System 2

Shiki Nanaya, a modern man transported to Taisho-era Japan, finds himself mistaken for the demon king Kibutsuji Muzan by the Demon Slayer Corps. Accompanied by A'Long, a sentient humanoid artifact and former mountain god who serves as his Noble Phantasm, Nanaya is actually a vessel for various Heroic Spirits summoned through a mysterious system. His primary mission is to locate and defeat Ibaraki Dōji, a powerful oni, in exchange for a fragment of the Holy Grail. Initially perceived as a demon due to his Western attire and A'Long's terrifying appearance, Nanaya clarifies the misunderstanding through combat with Love Hashira Uzui Tengen, proving his lack of killing intent and willingness to cooperate.

The narrative shifts to the Entertainment District, where Demon Slayers Tanjiro, Zenitsu, and Inosuke are investigating missing persons. Nanaya and A'Long intervene during a battle against Upper Rank Six demons, Daki and Gyutaro. Nanaya utilizes the persona of Sakamoto Ryoma, a historical figure, to gain trust and tactical advantage. He captures Daki and uses her as leverage to force Gyutaro into a confrontation. A'Long transforms into a colossal dragon to defeat Gyutaro, while Nanaya assists in subduing Daki. The victory is short-lived, as Muzan Kibutsuji kills Daki to silence her, revealing his surveillance over his subordinates. Despite this, the Demon Slayer Corps, including Water Hashira Giyu Tomioka, recognizes Nanaya's value and offers him an alliance.

Nanaya agrees to help the Corps hunt Muzan, provided they assist him in finding Ibaraki Dōji. He reveals that he will soon depart, replaced by another Heroic Spirit, Oda Nobunaga. The Master of the Demon Slayer Corps, Kagaya Ubuyashiki, accepts Nanaya's explanations and grants him trust, marked by a wisteria crest. Meanwhile, Muzan, enraged by the loss of two Upper Moons, orders all demons to find Sakamoto Ryoma and investigate his nature, driven by jealousy over Nanaya's ability to walk in sunlight. Nanaya, now embodying Oda Nobunaga, continues his hunt for Ibaraki, who is rumored to be a sun-resistant demon seeking Muzan.

Oda Nobunaga, accompanied by Uzui Tengen, tracks Ibaraki Dōji to a mountain. Their search is interrupted by the arrival of Upper Moon One, Akaza. Akaza, recognizing Nobunaga's divine nature, engages him in battle. Uzui is sidelined, unable to contribute significantly against such a powerful opponent. Akaza's interest lies primarily in Nobunaga, viewing him as a worthy adversary rather than a mere demon slayer. The encounter highlights the escalating threat as Muzan's elite forces actively hunt for the anomalies in their ranks. Nanaya, through Nobunaga, prepares to face Akaza, knowing that defeating or evading Upper Moon One is crucial for his mission and the safety of his allies. The story concludes with the tension between the Heroic Spirits, the Demon Slayer Corps, and Muzan's demons reaching a critical point, setting the stage for further conflicts involving Ibaraki Dōji and the ultimate confrontation with Muzan.