Arima Eiji, a police detective nearing retirement, who belongs to the Misjudgement Countermeasure Officer has had the experience of arresting the wrong person for a crime he did not commit. As such, when he is tasked to investigate the likelihood of wrong judgments given out to criminals on death row along with young lawyer Sera Shoichi and prosecutor Haruna Misuzu, Arima takes this on with the intention of repenting for his past mistake. On the other hand, although Sera is suspicious of Arima's actions, he is pushed along by the latter's passion to assist in the re-investigations while Haruna just wants to get back to the prosecutors' office as soon as possible so she has no choice but to obey the orders of her superior to cooperate with Arima and Sera.