"Gatchaman Crowds" is set in a near-future Japan where the city of Tachikawa is protected by a secretive team of heroes known as the Gatchaman. These heroes are chosen individuals who wield NOTE, a manifestation of their life energy, allowing them to summon powerful suits and combat alien threats. The story centers around Hajime Ichinose, an energetic and unconventional high school girl who is recruited into the Gatchaman team. Her unique perspective and unorthodox methods often clash with the more traditional and rigid approaches of her teammates, particularly Sugane Tachibana and Utsu-tsu, who struggle to adapt to her unpredictable nature.

The narrative explores the dynamics of the Gatchaman team as they face off against the MESS, mysterious alien entities that threaten the city. However, the primary conflict shifts when a charismatic and enigmatic figure named Berg Katze emerges. Katze is a shape-shifting alien with a penchant for chaos, manipulating events to sow discord and challenge the Gatchaman's ideals. Katze's actions are intertwined with the rise of GALAX, a social media platform that empowers citizens to take direct action in emergencies. While GALAX initially appears to be a force for good, its influence becomes increasingly ambiguous as it blurs the line between heroism and vigilantism.

As the story progresses, Hajime's unwavering optimism and belief in the potential of humanity become central to the team's efforts. Her interactions with the reserved and duty-bound Sugane, the pragmatic and tech-savvy Joe Hibiki, and the enigmatic alien Paiman highlight the diverse perspectives within the Gatchaman. The series delves into themes of individuality, societal responsibility, and the impact of technology on human behavior, particularly through the lens of GALAX and its creator, Rui Ninomiya, a young prodigy who seeks to redefine heroism.

The climax of the series revolves around the Gatchaman's confrontation with Katze and the unraveling of GALAX's true purpose. Hajime's ability to inspire others and challenge conventional thinking proves pivotal in resolving the conflict, ultimately leading to a resolution that emphasizes collaboration and the potential for positive change. The narrative concludes with a reflection on the evolving role of heroes in a world where technology and human agency are increasingly intertwined.