Tenn Kujō is an 18-year-old idol in the group TRIGGER. Originally born Tenn Nanase, he is the twin brother of Riku Nanase but was adopted into the Kujō family as a child, resulting in his legal removal from the Nanase family register and the formal severing of those familial ties.

His childhood involved significant personal sacrifice due to Riku's chronic illness. Tenn frequently cared for his brother, building snowmen outside Riku's window when he couldn't play outdoors and burning his fingers while making pancakes for him. He also took numerous photographs of Riku using a secondhand digital camera from their father, preserving the images digitally despite their separation. These experiences shaped Tenn's offstage personality, characterized by emotional detachment, a cold demeanor, and apparent indifference toward his own well-being. This contrasts sharply with his meticulously crafted stage persona, where he embodies perfectionism, striving for flawless performances 24 hours a day, 365 days a year to ensure fan satisfaction. He views idol work as a responsibility to bring hope through performance, stating an idol's job is to "sing, to smile" even amid despair.

Tenn's relationship with Riku displays outward hostility masking deep-seated protectiveness. After leaving the Nanase household, he debuted with TRIGGER partly to support Riku indirectly, initially concealing their connection. He treats Riku coldly in public and avoids direct communication, yet worries incessantly about Riku's health and secretly attends IDOLiSH7 concerts disguised as a fan. Riku reciprocates this hidden affection, often pausing TRIGGER DVDs to rewatch Tenn's solo scenes. Tenn harbors lingering jealousy from missing Riku's upbringing, though their later reconciliation allows him to express concern more openly, such as monitoring Riku's daily messages and intervening to resolve Riku's creative struggles during joint training sessions.

Within TRIGGER, Tenn frequently clashes with fellow member Gaku Yaotome over conflicting philosophies on idol authenticity—Gaku prioritizes genuine self-expression, while Tenn believes idols should prioritize audience perception even if it requires artifice. Despite this, Tenn respects his groupmates and prefers dialogue over confrontation. He demonstrates subtle care, watching their televised appearances promptly and enforcing professionalism during rehearsals. His dynamic with Ryūnosuke Tsunashi includes lighthearted moments, like repeatedly ejecting Ryūnosuke from group chats.

Tenn's personal habits reflect his disciplined yet self-neglectful nature. He schedules rigorous fitness routines like morning walks to watch sunrises, prepares weekly meals in advance for efficiency, and enjoys sugarcane chewing. His hobbies include visiting the amusement park Bandnamcoland, watching musicals, and consuming sweets like donuts. He dislikes hot baths and identifies with suama as a self-comparison. His ideal partner would understand the performing arts industry to avoid mutual unhappiness, and his dream date involves watching parades at an amusement park or relaxing at home.

Character development reveals Tenn's gradual softening. He assists IDOLiSH7's manager, Tsumugi Takanashi, by offering insights during TRIGGER's musical rehearsals and gifting her star-shaped konpeitō candy as a symbolic gesture of solidarity with IDOLiSH7. He also high-fived Mitsuki Izumi during a successful filming take, displaying uncharacteristic spontaneity. In reflective moments, he acknowledges his fear of performance errors and the emotional toll of maintaining perfection, revealing vulnerability beneath his composed exterior.