Tsukihara Kazuma, regarded by many as the greatest detective of all time, has landed on a unique case. That unique case involves his bestfriend, Nagato Minato, as the victim of a murder incident.

When Kazuma learned that his bestfriend was the victim, he was very angry to the point that when he catches the culprit, he will kill it.

But when he and his team went to the crime scene, a headache hits him and suddenly, he remembered what happen.

The truth is he, Tsukihara Kazuma, is the murderer.

After this realization, he surrenders to the authority.

After 2 weeks, at the court, where the judges give punishment to Kazuma, is being held. Here the judge questions Kazuma on what is his motive and reasons that he killed his bestfriend. But Kazuma, in the state of confusion and regret, don't know.

Suddenly, an idea popped on his head and ask the judge to give him a chance to investigate and learn the reason why he killed his bestfriend. The judge agrees, as he knows that it would be a big loss when they lost Kazuma, but Kazuma should have a partner that will help him in this case named "Black Fragment".

Here comes Nakamura Sakura, known as the 2nd best detective after Kazuma. She was assigned as Kazuma's partner regarding this case.

Together, they will find the cause of the "Black Fragment".

Is both of them enough to solve this unusual case?