Lin Ōtsuki is a key figure in the world of UniteUp! -Uni:Birth-. He originally performed as one half of the legendary idol duo Anela under the groovy Production banner, where he achieved immense popularity. An injury forced him to retire from active performance, prompting him to establish the sMiLea Production talent agency, through which he dedicates himself to discovering and training new idols.

His background includes experience as a child actor, which contributed to his high level of professionalism and persistent work ethic. Lin is known to be strict at times, often pushing those around him to strive for improvement, but he remains approachable and genuinely cares for the idols under his guidance. He balances this demanding side with a friendly and sometimes humorous demeanor, occasionally offering advice while casually using his smartphone.

Lin's motivation stems from a desire to nurture the next generation of performers, drawing on his own past successes and setbacks. He values hard work and discipline, yet also shows warmth and a protective attitude toward his trainees. In the narrative, he acts as a mentor and founder of the agency, providing both the institutional foundation and personal support that allow the story’s budding idols to grow. Key relationships include his former partner Maoto, with whom he formed Anela, and the various sMiLea Production idols whom he guides. His development involves transitioning from a celebrated performer to a behind‑the‑scenes leader, learning to balance his high standards with empathy. Notable abilities include his sharp industry insight and his capacity to recognize and cultivate talent, as well as his own past stage prowess—though his active performance days are behind him due to his injury.