Keena Soga is a central figure in the story, a student at Constant Magic Academy who presents a deceptively simple exterior while being intertwined with the fundamental laws of her world. She is a young woman with distinctive red hair often styled with several prominent tufts that resemble antennae, and brown eyes. She is typically seen wearing her school uniform and is rarely without a unique bird-shaped hairpin, a seemingly ordinary accessory that carries significant personal history.

Her background is rooted in childhood. The bird-shaped hairpin she always wears was a gift from Akuto Sai, given to her when they were both children living in an orphanage. This token forms a deep, unspoken bond between them. She later enrolls at the same magic academy as Akuto, becoming a classmate in 1-A.

In terms of personality, Keena is most often perceived as an airheaded and whimsical individual, with a pronounced obsessive love for white rice. Her dedication to rice is so extreme that she can distinguish its type and water quality simply by observing the steam from a cooker, and she secretly keeps a rice cooker in her dorm despite regulations. She often acts on bizarre or nonsensical conclusions and has a tendency to spout poetic or theatrical lines. This ditzy demeanor, however, masks a sharp and capable mind; she achieves excellent grades in all her academic subjects, even if she struggles with practical magic. She is deeply kind and pacifistic, believing that simple acts like sharing a meal could lead to world peace. She is also notably afraid of dogs.

Keena’s motivations are centered on Akuto Sai. Despite the world branding him as the future Demon King, she affectionately nicknames him "Aa-chan" and staunchly declares herself to be his "Demon Lord guard." Her primary drive is to protect him, often watching over him from the shadows and intervening when she senses he is in danger or being manipulated by others. Her pacifistic nature means she seeks to resolve threats without causing harm, often by using her unique abilities to evade or redirect danger rather than confront it directly.

Her role in the story is multi-layered. On the surface, she is the quirky, devoted friend and love interest who provides comic relief and unwavering support for Akuto. Beneath this, she is a mysterious and powerful observer who seems to know far more than she lets on. She frequently appears at critical moments, often in the nude after her invisibility spell fails, leading to recurring comedic situations. Her true significance, however, is her connection to the "Law of Identity," a transcendent and fundamental principle of reality that governs existence itself. She shares her existence with this entity, acting as its primary vessel or incarnation, though their personalities and knowledge are vastly different. This makes her a target for those who fear such power and a key to the world's deepest mysteries.

Key relationships define her actions. Her most important relationship is with Akuto Sai, whom she loves and is utterly devoted to protecting. She shares a close, if occasionally exasperated, friendship with her fellow classmates, particularly the more serious Junko Hattori, with whom she often interacts. Her unique nature also draws the attention of teachers and other powerful figures who are aware of her true significance.

Keena undergoes significant development as the narrative progresses. Initially seen as merely a clumsy and eccentric girl, her role deepens as hints of her true nature and power begin to surface. After the death of the previous Empress, Kazuko, the Three Sacred Treasures of the realm choose Keena as her successor, and she is reluctantly elevated to the position of Empress of Japan. Despite inheriting immense power and authority, she largely ignores her imperial duties, preferring to follow her own whims and continue protecting Akuto. Ultimately, her development involves a merging or reconciliation with her identity as the Law of Identity, allowing her to transcend her initial limitations.

Her notable abilities are both limited and limitless, a direct reflection of her dual nature. In her everyday form, she possesses only two magical talents. The first is flight, the ability to levitate and move through the air. The second is a specialized form of invisibility that allows her to hide her body and mana signature completely; however, this power does not extend to her clothing or her hairpin, which remain visible, hence her frequent nude appearances. Aside from these, she is practically incapable of performing any other standard magic.

As the vessel of the Law of Identity or in her role as Empress, her true abilities are reality-defying. She has access to the "virtual alternate dimension," an infinite space where she can manipulate time and space, change the rules of reality, and banish enemies. She can wield the Imperial Regalia, powerful artifacts that grant abilities like creating homing energy spheres, generating a sword of intense heat, and even suppressing the power of the Demon King himself. At her highest level, she embodies the Law of Identity, the origin of all things. In this state, she exists beyond linear time and dimensions, with the ability to perceive and manipulate all of reality as if it were a story. This grants her nigh-omnipotence, including conceptual manipulation, regeneration, and a form of immortality where she will continuously reincarnate as long as the fundamental concept of identity exists. Despite this cosmic power, her combat skill remains low in her default state, as she does not instinctively know how to use her abilities for fighting and prefers non-violent solutions.