In "Gravion," humanity faces an existential threat from the Zeravire, mysterious alien entities that emerge from another dimension. To combat this menace, the wealthy and enigmatic Eiji Shigure assembles a team of pilots to operate the Gravion, a massive super robot composed of smaller mecha units. The story centers on Eiji's adopted son, Toga Tenkuji, a skilled but reluctant pilot who joins the team after his sister is abducted by the Zeravire. Alongside Toga, the team includes a diverse group of pilots, each with unique personalities and skills, such as the stoic Sandman, the cheerful Mizuki Tachibana, and the enigmatic Leele.

The narrative unfolds as the team battles the Zeravire in increasingly intense confrontations, uncovering the true nature of the alien threat and its connection to Eiji's past. The Zeravire's attacks grow more sophisticated, forcing the team to adapt and strengthen their bonds to unlock the Gravion's full potential. As the story progresses, secrets about Eiji's motivations and the origins of the Zeravire are revealed, adding layers of intrigue and complexity to the plot. The series balances action-packed mecha battles with character-driven drama, exploring themes of sacrifice, loyalty, and the cost of protecting humanity.

The first season, "Gravion," sets the stage with the team's formation and initial battles, while the second season, "Gravion Zwei," delves deeper into the overarching mystery, culminating in a climactic showdown that resolves the conflict with the Zeravire. Throughout the series, the interplay between the characters and their evolving relationships adds emotional depth to the high-stakes battles, creating a compelling narrative that blends mecha action with personal drama.