Jaken is a small, green-skinned imp demon who serves as the loyal and self-proclaimed chief retainer to Sesshōmaru, a powerful dog demon. His background reveals that he was once the ruler of his own imp tribe in the Musashi Province, but after his people were nearly slaughtered by a powerful demon, Sesshōmaru appeared and destroyed the attacker, saving Jaken’s life. Instantly captivated by Sesshōmaru’s immense strength and beauty, Jaken pledged an oath of eternal loyalty to him. In return, Sesshōmaru granted Jaken a magical weapon known as the Nintōjō, or the Staff of Two Heads, allowing him to become his servant.

Jaken’s entire personality is defined by his extreme devotion to Sesshōmaru. He constantly praises his master’s greatness, acts as though every success was exactly as planned, and becomes deeply flustered or panicked on the rare occasions Sesshōmamaru faces a challenge in battle. Despite his boasts of having served for centuries and traveled across worlds, Jaken is notably cowardly and weak for a demon. His survival instincts often lead him to seek excuses to flee from danger, though his loyalty ultimately keeps him by his master’s side. He is also quite knowledgeable about various subjects, but his tendency to explain things in an arrogant and condescending manner means few take him seriously.

His primary motivation is to serve Sesshōmaru faithfully and to one day become the Chief Minister of the grand empire he believes his master will one day establish. Jaken takes great pride in his position, even if it often puts him in terrifying or humiliating situations. He is also deeply invested in seeing Sesshōmaru succeed, particularly in obtaining the powerful sword Tessaiga from his master’s half-brother, Inuyasha.

Within the story’s narrative, Jaken acts as Sesshōmaru’s constant companion, messenger, and comic relief. He is often tasked with carrying out errands, providing information, and, much to his annoyance, looking after a young human girl named Rin. Despite his servile role, Jaken has a surprisingly broad skill set. He wields the Staff of Two Heads, which has the face of an old man capable of spewing powerful flames that can annihilate groups of human soldiers or minor demons in an instant, and the face of a woman that shrieks to indicate when they are on the wrong path. The staff also has detection abilities and can generate barriers.

Jaken’s most significant relationship is with Sesshōmaru. His loyalty is absolute, born from a debt of gratitude and genuine admiration. For his part, Sesshōmaru keeps Jaken around, and despite frequently threatening to kill him for his failures or incessant chatter, he has never followed through. In a pivotal moment that contradicts his cold exterior, Sesshōmaru used the Tensaiga to resurrect Jaken after he was killed by the swordsmith Kaijinbō, an act that deeply moved his servant.

His relationship with Rin evolves considerably over time. Initially, Jaken dislikes her because she is human and resents being forced to act as her protector. However, as they spend more time together, he grows to genuinely care for her wellbeing, even as he continues to complain. He worries when she is in danger, risks his life to defend her, and when she dies in the netherworld, he is shown openly weeping. For her part, Rin respects Jaken, calling him Master Jaken and showing him kindness.

Jaken has a bitter and antagonistic relationship with Inuyasha, fueled by the conflict between the two brothers. He frequently devises schemes to steal Tessaiga for Sesshōmaru, all of which backfire spectacularly, often resulting in physical comedy. He also dislikes the monk Miroku, having been threatened by his Kazaana wind tunnel, and shows some sympathy for the young fox demon Shippō, as both are small and often bullied.

In terms of development, Jaken begins as a resentful servant who merely follows orders, but he gradually becomes a more complex figure. He learns to care for Rin, moving from grudging tolerance to genuine affection and grief at her loss. His loyalty is tested and proven genuine on multiple occasions, demonstrating that his service is more than just self-preservation. Despite his cowardice, he consistently chooses to stand by Sesshōmaru, even pleading to be allowed to follow him into incredibly dangerous battles.

Beyond his staff and limited flame attacks, Jaken possesses other notable abilities from his demon heritage. He is physically stronger than his small size would suggest, as he easily wields the Staff of Two Heads, which is much larger than himself. He also has some skill in illusion-casting and, in later events, is shown to be capable of creating a powerful barrier that can completely block the detection of demonic energy.