"Nikoichi!!" centers around the life of Nikoichi, a young man with an extraordinary ability to sense danger before it happens. This premonition-like skill, which he refers to as his "danger radar," allows him to avoid accidents, confrontations, and other perilous situations. Despite this unique gift, Nikoichi lives a relatively ordinary life, working a mundane job and trying to stay under the radar. However, his quiet existence is disrupted when he encounters a mysterious girl named Yuki, who is being pursued by a shadowy organization.

Yuki possesses her own unique ability: she can manipulate time in short bursts, allowing her to rewind events by a few seconds. This power makes her a target for the organization, which seeks to exploit individuals with supernatural talents for their own gain. Nikoichi reluctantly becomes involved in Yuki's plight, using his danger radar to help her evade capture. As the two form an uneasy alliance, they uncover a larger conspiracy involving the organization's experiments on people with extraordinary abilities.

The narrative unfolds as Nikoichi and Yuki navigate a series of high-stakes encounters, facing off against agents of the organization and other individuals with powers. Along the way, they encounter allies who also possess unique abilities, such as a man who can manipulate fire and a woman with enhanced physical strength. These characters join forces with Nikoichi and Yuki, forming a makeshift team to combat the organization's growing threat.

As the story progresses, Nikoichi's danger radar evolves, becoming more precise and allowing him to anticipate larger-scale threats. This development proves crucial as the group uncovers the organization's ultimate goal: to create a weapon capable of harnessing and amplifying supernatural abilities on a global scale. The stakes escalate as Nikoichi and his allies race to prevent the organization from achieving their objective, leading to a climactic confrontation that tests the limits of their powers and resolve.

Throughout the series, the dynamics between the characters are explored, particularly the growing bond between Nikoichi and Yuki. Their relationship evolves from one of mutual necessity to genuine trust and camaraderie, with both characters relying on each other's strengths to overcome challenges. The narrative also delves into the moral implications of their abilities, questioning the ethics of using such powers for personal gain or to manipulate others.

"Nikoichi!!" balances action-packed sequences with moments of character development, creating a story that is both engaging and thought-provoking. The manga explores themes of trust, sacrifice, and the consequences of wielding extraordinary abilities, all while maintaining a fast-paced and suspenseful plot. The interplay between the characters' powers and their personal struggles adds depth to the narrative, making it a compelling read for fans of supernatural and action-oriented manga.