Tenn Kujo forms the core of the idol group TRIGGER, captivating audiences with an angelic stage presence defined by flawless performances and a dedication to spreading joy through song and smiles, even in dark times. Offstage, he reveals a starkly contrasting persona: cold, callous, and emotionally restrained, often appearing indifferent to his own well-being. This detachment originates from profound worry over his twin brother, Riku Nanase, who battles a chronic respiratory illness. While masking significant inner turmoil, Tenn maintains professionalism, resolving conflicts through dialogue rather than confrontation, especially with TRIGGER member Gaku Yaotome, with whom he frequently clashes over artistic integrity versus fan service.

Five years before the main events, Tenn severed all ties with the Nanase family, legally changing his surname to Kujo and removing himself from the family registry to protect Riku, causing prolonged estrangement. He concealed his deep affection and concern for his brother, even feelings of jealousy over missing Riku's childhood. His initial reason for joining TRIGGER was explicitly for Riku's benefit, a secret he kept. Despite outwardly dismissing their relationship, Tenn secretly kept childhood mementos, like digital photos of Riku taken with a camera from their father. Past actions—building snowmen by Riku's hospital window or burning his fingers making pancakes for him—further demonstrate this hidden care.

Tenn's recruitment into TRIGGER was orchestrated by producer Takamasa Kujo during a vulnerable period, leveraging promises of support Tenn later recognized as manipulative tactics also used on others, including Aya, Tamaki Yotsuba's sister. This realization caused him significant distress, especially when hearing the same promises offered to new recruits, forcing him to confront the transactional nature of his adoption and career. Subsequent interactions with Riku gradually thawed his emotional reserve, leading to a cautious reconciliation where both acknowledged their bond without lingering resentment.

In daily life, Tenn adheres to strict routines: morning walks for sunrises and meticulous meal preparation. He enjoys cats, sugarcane, donuts, omurice, and J-Pop, but dislikes hot baths. He secretly attends IDOLiSH7 concerts disguised to watch Riku, watches TRIGGER's broadcasts promptly, and frequents Bandnamcoland amusement park. Tenn also repeatedly removed Ryunosuke Tsunashi from TRIGGER's group chat, reflecting his selectively assertive nature. Professionally dedicated to perfectionism, his reconciliation with Riku allows subtle shifts toward valuing personal connections over unwavering self-sacrifice.