"Crazy Gate" centers on a mysterious phenomenon where a series of ancient gates suddenly appear across the world, each leading to a different dimension filled with fantastical creatures, advanced technology, and untold dangers. The gates are linked to an ancient civilization that once thrived on Earth, and their reappearance triggers a global crisis as governments, organizations, and individuals scramble to understand and control them. The story primarily follows a group of unlikely allies who are drawn together by fate, each possessing unique abilities tied to the gates.

The protagonist, Kaito, is a high school student who discovers he has the rare ability to manipulate the gates, allowing him to open, close, or even alter their destinations. His power attracts the attention of both benevolent and malevolent forces, including a secretive organization known as the Gatekeepers, who seek to protect humanity from the threats emerging from the gates, and a rogue faction called the Eclipse, which aims to exploit the gates for their own gain. Kaito is joined by a diverse cast of characters, including Rin, a skilled fighter with a tragic past tied to the gates; Haruto, a scientist specializing in interdimensional physics; and Mei, a mysterious girl who claims to have originated from one of the gate dimensions.

As the group navigates the dangers of the gates, they uncover a deeper conspiracy involving the ancient civilization that created them. The gates were not merely portals but part of a larger system designed to test and evolve humanity. The civilization's ultimate goal was to determine whether humanity could coexist with the other dimensions or if it would succumb to greed and destruction. The series explores themes of trust, sacrifice, and the consequences of wielding power, as Kaito and his companions face moral dilemmas and personal challenges while trying to prevent a catastrophic collision of dimensions.

The narrative is structured around episodic adventures through various gate dimensions, each with its own unique environment and challenges, while an overarching plot ties these experiences together. The characters' relationships and backstories are gradually revealed, adding depth to their motivations and actions. The series balances action, mystery, and emotional moments, culminating in a climactic confrontation that determines the fate of both Earth and the interconnected dimensions.