"Mobile Suit Gundam ZZ" is the direct sequel to "Mobile Suit Gundam Zeta," set in the Universal Century timeline. The story begins shortly after the events of its predecessor, with the Earth Federation and the remnants of the Neo Zeon movement, led by Haman Karn, continuing their struggle for dominance. The protagonist, Judau Ashta, is a teenage junk collector living in the space colony of Shangri-La. Unlike previous Gundam protagonists, Judau is initially more carefree and less politically motivated, but his life changes when he encounters the Argama, a ship carrying the Zeta Gundam and its successor, the ZZ Gundam.

Judau and his friends, including his younger sister Leina, are drawn into the conflict after Neo Zeon forces attack their colony. Judau pilots the ZZ Gundam, a powerful mobile suit capable of transforming and combining with other units, to protect his friends and fight against Neo Zeon. The Argama's crew, including veterans like Bright Noa and returning characters such as Elpeo Ple and Ple Two, provide support and guidance as Judau grows into his role as a pilot and leader.

The narrative explores themes of war, loyalty, and the impact of conflict on individuals and communities. Judau's journey is marked by his evolving understanding of the war's stakes and his relationships with those around him. Key antagonists include Haman Karn, who seeks to restore Zeon's glory, and Mashymre Cello, a loyal Neo Zeon officer with a personal vendetta. The story also delves into the complexities of Newtypes, individuals with heightened psychic abilities, and their role in shaping the future of humanity.

As the conflict escalates, Judau and his allies face numerous battles across Earth and space, culminating in a decisive confrontation with Neo Zeon. The series balances intense mecha action with character-driven moments, highlighting the personal struggles and growth of its cast. By the end, Judau emerges as a more mature and determined figure, having faced the harsh realities of war and the responsibilities of wielding immense power. "Mobile Suit Gundam ZZ" serves as a bridge between the events of "Zeta Gundam" and the later "Char's Counterattack," contributing to the overarching narrative of the Universal Century timeline.