Shu Izumi leads and produces the idol unit QUELL under TSUKINO TALENT PRODUCTION. He possesses light brown hair, light blue eyes, and three earrings—two in his left ear and one in his right. His calm, refined demeanor often leads people to mistake him for older than he is, a perception that sometimes bothers him. Described as "gently powerful, cooly passionate," he shows strong leadership and a protective instinct, especially towards younger members. His childhood was complicated and difficult. As a teenager, he belonged to a highly popular national idol group alongside Shiki Takamura (SolidS), Takaaki Mamiya (VAZZY), Rei and Roa (infinit0), and two others. Creative differences caused the group's disbandment, starting with Shiki's departure. In June 2015, Shu met Eichi Horimiya, an assistant director, during drama filming. They became close friends, communicating and meeting frequently. During a late March or early April 2016 press tour in Sapporo, Shu encountered orphaned twins Issei and Ichiru Kuga. Moved by their situation, he brought them to Tokyo and introduced them to TSUKINO PRODUCTION's president, facilitating their idol debut. At this meeting, Shu invited Eichi to be QUELL's manager; Eichi panicked but accepted. Later, the twins suggested Eichi join as an idol due to his dancing skills. Shu endorsed the idea, finalizing QUELL as a four-member unit. Shu is deeply protective and nurturing towards the twins. Learning they rarely ate cake except on birthdays, he began buying it for them regularly with "no particular reason." He bonds with Issei over shared interests like reading and recommends books, though only Issei reads them. He spoils them with expensive gifts, reflecting his poor grasp of monetary value from his long idol career. His relationship with Eichi features mutual trust and equality. Shu admires Eichi's empathy and fan-connecting ability, considering it rare in entertainment. Eichi supports Shu practically, preparing stomach-friendly meals for late work nights. They collaborate professionally: Eichi handles logistics while Shu focuses on musical composition and leadership. Shu maintains a longstanding friendship with Shiki Takamura despite their group's past disbandment. They frequently meet for soba, though Shu drinks tea instead of alcohol due to intolerance. He also shares ties with Rikka Sera (SolidS), likely from Rikka's modeling background. His connection with former groupmate Takaaki Mamiya has weakened. Personal habits include visiting shrines and temples for their calming atmosphere, meditating, and appreciating plants and forests, influencing QUELL's apartment decor. He enjoys cheesecake and making white sauce. Debuting young, he never held a part-time job. He has a high tolerance for horror but cannot handle alcohol or cigarettes. Across QUELL's activities, Shu composes songs described as "prayers," reinforcing his image as a grounding force. His leadership blends charisma and levelheadedness, emphasizing family-like unity. This dynamic earned QUELL the nickname "kazoquell." His development involves navigating protective instincts while encouraging the twins' independence and fostering Eichi's growth from manager to performer. In broader media, QUELL maintains a friendly rivalry with SolidS, partly from Shu and Shiki's history. Stories involving the unit often conclude positively, reflecting Shu's role in resolving conflicts and maintaining harmony. His 2021 catchphrase, "Where there is a will, there is a way," underscores his persistent, solution-oriented mindset.