Owl is a master shinobi and the central antagonist in the story of Sekiro. Known as the Great Shinobi Owl, he serves as the adoptive father and mentor to the protagonist, Wolf. His past is shrouded in mystery, though it is known that he originated from the Usui forest, a place of mist and illusions, and he shares a long history with Lady Butterfly, having been friends with her since childhood. It was on a battlefield following Isshin Ashina's rebellion that Owl discovered a young orphaned boy, Wolf, and was impressed by his fierce will to survive. Taking the boy in, Owl raised him as his own son and trained him ruthlessly in the arts of the shinobi.

Owl is defined by his immense ambition, cunning, and manipulative nature. He is a rogue shinobi driven by a relentless desire for power and greatness, with little regard for the lives he destroys in pursuit of his goals. While he presents a facade of a stern but honorable father, his actions reveal a deeply treacherous and self-serving core. He respects strength above all, and his interactions are often calculated attempts to deceive or control those around him. There is a faint, complex thread of paternal pride in Wolf's accomplishments, but this is consistently and brutally overridden by his own selfish ambitions. He adheres to a strict personal doctrine known as the Iron Code, which dictates that the parent's will is absolute and must be obeyed, a rule he uses to command his son's loyalty even as he himself breaks all other bonds of trust.

Owl's primary motivation is to obtain the power of the Dragon's Heritage, the sacred bloodline of his master, the young Lord Kuro. He sees the immortality this heritage grants not as a divine gift but as a tool to seize political and military control of Japan. Unlike other characters who seek the power for a noble cause, Owl's desire is purely for personal glory and domination. His role in the story is that of a hidden puppeteer, revealed to have orchestrated the attack on the Hirata Estate years prior. He faked his own death in the ensuing chaos, stabbing Wolf in the back to cover his tracks, all as part of a larger scheme to claim Kuro for himself.

The most critical moment in Owl's relationship with Wolf occurs atop Ashina Castle. After Wolf gathers the components for the divine aroma, Owl confronts Lord Kuro and presents his son with an impossible choice. He commands Wolf to obey the Iron Code, forsake Kuro, and join him in his quest for power. If Wolf refuses, Owl reveals his true, murderous intent and attacks his own son. If Wolf instead chooses to obey, Owl leaves him to deal with the consequences and later returns, having killed Genichiro and taken the Black Mortal Blade. In this scenario, Owl's triumph is short-lived, as Wolf, fully transformed into a Shura, kills him from behind. Through a special memory, Wolf can also revisit the night of Hirata Estate's downfall and face a younger, more powerful version of his father in a final, purifying confrontation.

As a fighter, Owl is a formidable and dishonorable opponent, reflecting his shinobi philosophy. His abilities are a mix of raw strength and underhanded tactics. He wields a massive katana with devastating power but relies heavily on trickery. He employs smoke pellets to vanish from sight, scatters pellets that heal him, and throws shurikens. He can also deploy a powerful anti-healing bomb that prevents the use of healing gourds. His signature technique involves stomping on his opponent to cancel their attacks, a move that embodies his cruel and dismissive nature. In his prime form, he gains access to mystical abilities such as turning into a ghostly owl, and he can conjure magical fire, making him an even more lethal and deceptive adversary.