Ron Kamonohashi, the best student in the history of the elite Detective Training Academy BLUE, has been living as a recluse since BLUE expelled him five years ago. Moreover, he is forbidden to work as a detective, having barely escaped execution after getting involved in a murder case while he was still attending the school. Ron's situation changes drastically when police detective Totomaru Isshiki, following the advice of a senior colleague, seeks him out for help with a criminal case that has remained unsolved for months. Ron reluctantly agrees to help Totomaru and uses his phenomenal intuition to discover the culprit in less than a day. However, it appears that Ron suffers from a mysterious condition that can cause those around him to lose their lives. To Ron's great surprise, Totomaru manages to save the life of someone whom Ron put in jeopardy.

As the unlikely duo starts solving crimes one after another, BLUE sends operatives after its former student to find out if he has resumed investigative work. Fighting against murderers, rogue detectives, and the Metropolitan Police Department, Ron and Totomaru must join forces if they want to survive and see justice prevail.