Agino Jiro is a brilliant scientist specializing in temporal physics, driven by profound grief over his wife Haruno's death in a traffic accident. Unable to accept her loss, he dedicates himself obsessively to building a functional time machine. His sole purpose is to travel back and prevent Haruno's accident, hoping to reclaim his shattered happiness. This relentless pursuit consumes him, isolating Jiro as he channels all resources into the project.

After years of intense work, Jiro succeeds. He activates the machine, transporting himself to the year 2015. There, he encounters a young woman named Haruka. He learns Haruka is his daughter, born after his departure into the future. Raised by others in this altered timeline, she possesses deep knowledge of temporal mechanics and warns of the dangers of altering the past.

Haruka actively opposes Jiro's plan to save Haruno. She explains that changing the accident would create a paradox, erasing her existence and risking catastrophic timeline instability. Haruka embodies the unintended consequence of Jiro's actions.

Faced with Haruka's existence and her pleas, Jiro experiences a deep internal conflict. His desperate desire to save Haruno clashes with the reality of his unknown daughter and the potential disaster.

The confrontation forces a pivotal decision. Jiro chooses not to save Haruno. Recognizing the paramount importance of Haruka's life and timeline stability, he sacrifices his chance for reunion.

Jiro returns to his original time using the machine. Upon arrival, he immediately destroys the time machine, ensuring no one can ever attempt such temporal manipulation again. This act signifies his acceptance of Haruno's death and his commitment to living in the present, carrying the memory of both his wife and the daughter he met from the future.