Tenten Koganei is the eldest of five children adopted into the martial arts Koganei clan, associated with the Chinese zodiac tiger. Her undisclosed biological origins likely stem from orphan status, though the clan prioritized her exceptional combat potential and efficiency when integrating her into the main family.

Physically 18 years old, she stands 165 cm tall with blonde hair typically in twin pigtails, green eyes, and occasional freckles. Her signature attire is a bright red, figure-hugging Chinese-style silk dress exposing the sides of her legs and thighs.

Her personality exhibits intense sadism, paranoia, and possessiveness. She eliminates subordinates perceived as disloyal without hesitation and doses male followers with mind-control drugs to ensure absolute obedience, deriving pleasure from their psychological torment. Skilled acting maintains a deceptive facade of politeness and sweetness; she presents a smiling, lovely-girl persona to lower others' guard, masking her true manipulative and "devilish" nature. This masking originates from deep-seated insecurity and an inability to express genuine emotions, causing frustration when others fail to discern her hidden feelings. Despite her cruelty, she adheres to a personal code of honor, such as providing authentic antidotes when defeated.

Her background involves infiltrating the Miyamoto clan under the guise of friendship with Inaho Miyamoto. She feigned a sisterly bond ("Tenten-neesan") while systematically manipulating and stealing their manpower to bolster the Koganei clan for their role in assassinating Koushi Inuzuka. Resentment toward Inaho intensified upon discovering Hanzo, a figure she developed feelings for, had become Inaho's loyal subordinate.

In combat, Tenten wields formidable abilities. She simultaneously channels dual battle auras—Tiger and Snake styles—using one aura to neutralize an opponent's defenses while the other attacks. Expertise in chemistry and poisons led her to refine a deadly undetectable toxin and create mind-altering drugs for control. Preferring manipulation over direct confrontation, she remains unafraid to engage physically, overwhelming opponents like Hanzo and Inaho.

Key relationships define her conflicts. Within the Koganei clan, she demonstrates pragmatic loyalty, collaborating particularly with Tenrei. Her interactions with Hanzo began neutrally when she guided him as a "lost guest." He uniquely perceived her concealed anger, sparking unexpected emotional vulnerability and a crush. This attraction twisted into obsessive jealousy during battles; she tormented Hanzo and Inaho to vent frustration over their bond, nearly stabbing Hanzo in rage. Her envy of authentic relationships, contrasted with her own transactional connections, culminated in silent retreat after her schemes failed, acknowledging defeat by giving Hanzo the antidote.

Subtle development hints at underlying fragility. Moments of shock—Hanzo seeing through her mask, witnessing Mokona defend a rival, or seeing subordinates defy her control—revealed gaps in her understanding of human bonds. These instances exposed jealousy and longing for genuine connections she lacked, particularly highlighted by Hanzo's consistent perception of her true emotions, which deeply unsettled her controlled demeanor.