"IDOLiSH7 Third Beat!" continues the journey of the idol group IDOLiSH7 as they navigate the challenges of the entertainment industry while striving to achieve their dreams. The series picks up after the events of the second season, with the group gaining increasing popularity and recognition. However, their success comes with new pressures, including intense competition, personal struggles, and the complexities of maintaining their unity as a team.

The narrative delves deeper into the individual backstories and motivations of the members, revealing their vulnerabilities and growth. Riku Nanase, the group's center, faces health issues that threaten his ability to perform, forcing him to confront his limitations and the fear of letting his teammates down. Meanwhile, Tenn Kujo, Riku's estranged twin brother and a member of the rival group TRIGGER, grapples with his own feelings of guilt and responsibility toward Riku, adding emotional tension to their relationship.

The series also explores the dynamics within TRIGGER, particularly the strained relationship between Gaku Yaotome and Ryunosuke Tsunashi, as they struggle to reconcile their differing visions for the group's future. The introduction of new characters, such as the members of the up-and-coming group Re:vale, further complicates the competitive landscape, as alliances and rivalries shift.

As IDOLiSH7 prepares for a major performance at the Budokan, the stakes are higher than ever. The group must overcome internal conflicts, external pressures, and personal doubts to deliver a performance that will solidify their place in the industry. The series balances moments of intense drama with lighthearted camaraderie, showcasing the bonds of friendship and determination that drive the characters forward.

Throughout the season, themes of perseverance, self-discovery, and the pursuit of dreams are central to the narrative. The characters' growth is portrayed through their interactions, performances, and the challenges they face, highlighting the sacrifices and rewards of life as an idol. "IDOLiSH7 Third Beat!" maintains a focus on the emotional and professional journeys of its characters, offering a compelling continuation of the IDOLiSH7 saga.