Ju Fa, also known by the moniker Great Emperor Akshobhya, is a major antagonist in the story. He is one of the seven rulers of Kotaku, the mysterious island at the center of the narrative, and a member of a group of immortal beings known as Lord Tensen. His existence began roughly one thousand years ago, as he and the other Tensen were unknowingly born from the Tao, a form of spiritual energy, of a puppet created by their leader, Rien, during her research into eternal life.

Ju Fa has a distinct and fluid appearance. He is often initially encountered in a female-presenting form, referred to as his Yin form, characterized by shoulder-length blonde hair and blonde irises. In this guise, he may appear shirtless or wear pale yellow and white robes. However, his personality is more commonly associated with his male-presenting Yang form, which he frequently switches to during combat or when angered. His attire typically includes a pale yellow haori, a beaded necklace with a golden flower amulet, a black hanfu, a white hakama, and black boots.

The core of Ju Fa’s personality is defined by an intense, century-spanning devotion to his partner, Tao Fa. Their relationship is both sibling-like and romantic, forged over centuries of shared existence. Ju Fa is fiercely protective of Tao Fa, and he cannot bear to see her harmed, even though their regenerative abilities make them nearly immortal. This loyalty stands in stark contrast to his demeanor toward the outside world. He is extremely short-tempered, aggressive, and hostile, particularly toward humans, whom he despises and views as nothing more than livestock or tools to be used for the Tensen's purposes. He is quick to irritation, especially when a human proves to be a challenge in combat, and he becomes enraged by anything that disrupts his peace or threatens his partner.

Ju Fa’s motivations are intrinsically linked to his role as a member of Lord Tensen. The collective goal of the Tensen is to achieve perfect immortality and create the legendary Elixir of Life. To this end, they lure humans to the island of Kotaku, transforming them into beings called Tan to use as a source of life force. Within this brutal system, Ju Fa’s personal drive is the preservation of his bond with Tao Fa. Flashbacks reveal that their world is one of madness, where they were forced to endure harsh training and practices like Bochu Jutsu to mature their bodies and refine their Tao. While other Tensen grew indifferent to the suffering around them, Ju Fa cared deeply for Tao Fa, and he protected her from the worst of their existence, believing the world itself was insane, not them. His tragic motivation is to protect Tao Fa’s smile and remain by her side within a corrupt and desperate system.

In the story, Ju Fa is first encountered by the Aza brothers, Chobei and Toma. He initially appears in his female form with Tao Fa, but upon being discovered, he shifts to his male form and attacks, easily defeating the two bandits and tossing them into a pit. He later participates in meetings among the Lord Tensen to discuss the human invaders. Ju Fa looks down on the humans as inferior, a view that puts him in direct conflict with the main characters. His most significant role comes during the final confrontation in the Horai palace, where he and Tao Fa are forced to merge into a monstrous, fused Kishikai form after being pushed to their limits by a coalition of human fighters, including the Aza brothers, Gantetsusai, and Yamada Asaemon Fuchi. This fusion, the embodiment of their twisted love, becomes the central obstacle the humans must overcome.

Ju Fa’s key relationship is exclusively with his partner, Tao Fa. They are described as two halves of a whole, having been born together and remaining at each other’s side for a millennium. His development is tragic; while his bond with Tao Fa gives him empathy that other Tensen lack, it is ultimately the same bond that leads them to sacrifice their individual identities by fusing into a horrific, single-minded monster when death is near. In his final moments, after being defeated by the combined efforts of the human party and having his regeneration blocked by Water Tao, his last act is to apologize to Tao Fa for failing to protect her. She reassures him, expressing gratitude that he was her partner.

Ju Fa possesses a vast array of supernatural abilities. As a Tensen, he has complete mastery over Tao, specifically the Fire attribute. He can sense the presence and weak points of others, enhance his physical attacks, and launch invisible projectiles of Tao from a distance, a technique called Toate. All Tensen possess Flower Tao, a powerful regeneration ability that allows them to heal from almost any wound, including decapitation. The only way to permanently kill Ju Fa is to completely destroy the plant ovule located within his tanden, the spiritual core of his body, preferably using the opposing element of Water Tao. He is also capable of switching between his male Yang and female Yin forms to augment his power. His ultimate technique is the Kishikai transformation. Unlike other Tensen, Ju Fa must fuse with Tao Fa to achieve this state. The resulting form is a large, bulbous, heart-like body with wings made of petals, multiple faces, and vine-like appendages. In this form, they can fly, release devastating sonic shrieks, and fire countless spores that induce uncontrolled laughter in their opponents. However, this transformation is incredibly taxing on their Tao reserves and can only be maintained for a maximum of thirty minutes at a time.