Ensei Rō, also known as Ro Ensei, is first introduced in the narrative as a disheveled man with messy hair and a thick beard, a haggard appearance that causes him to be frequently mistaken for a kidnapper. Once he is persuaded to shave, he is revealed to be a handsome man in his late twenties with a distinctive cross-shaped scar located below his left eye. His background is marked by profound tragedy, as his entire clan was massacred by the Satsujinzoku, a violent gang in Sa Province. Following this trauma, he joined the gang himself, where he earned the moniker Little Staff King for his skill with pole weapons, though his true combat mastery is later noted by Shi Seiran to be in close-range unarmed combat.

At the age of seventeen, Ensei was appointed as the temporary governor of Sa Province under unprecedented circumstances declared by the noble Taiho Sa Enjun, which stated that anyone who thwarted an assassin would be given the position. He successfully maintained order and foiled assassination attempts during his tenure. However, after Sa Enjun’s death, Ensei’s political backing diminished, and his legitimacy as governor waned. He left Sa Province to assess the governance of Emperor Ryuuki and to request a replacement governor. During his journey to the capital, he faced repeated attacks from assassins and thieves drawn by a bounty placed on him by the Sa family, eventually collapsing from exhaustion near Shuurei Kou’s estate in Kiyou, where she took him in and cared for him.

Ensei’s personality is characterized by a gentle and humorous demeanor that serves as both comic relief and a source of emotional support for those around him. Despite his tragic past and the hardships he has endured, he maintains this outward calm and wit. After Shuurei’s term as governor of Sa Province concludes, Ensei becomes her assistant in the Censorate, driven by a deep admiration for her ideals and determination. He evolves into her closest confidant, understanding her pragmatic nature and goals even better than her longtime protector, Seiran. He supports her during critical missions, such as confronting the occult forces of Jyasenkyou and navigating the complex bureaucratic challenges of the imperial court.

His key relationships are deeply significant. He shares a complex and somewhat tense history with Shi Seiran, rooted in their mutual involvement with the Satsujinzoku. Their interactions are often marked by irritation, particularly from Seiran, yet there is an underlying current of respect between the two former comrades. Ensei also harbors unrequited romantic feelings for Shuurei, a sentiment he largely leaves unspoken but which is recognized by other characters such as Shin Suou. The depth of his bond with Shuurei is demonstrated when he helps her overcome a lifelong fear of summer storms, an achievement her own family had not managed. Later, she demonstrates her ultimate trust in him by entrusting him with a key to her awakening when she is placed in a life-threatening magical stasis by the Hyou clan. Ensei’s development throughout the story traces his transition from a provincial governor whose position is no longer secure to a dedicated public servant in the capital, with his journey reflecting a steadfast commitment to the stability of Saiunkoku and a devoted loyalty to Shuurei’s aspirations. His notable abilities include his expertise with a pole weapon, his mastery of unarmed combat, and his perceptive understanding of political situations and personal relationships.