Both playful detective Yamashita and the serious Tashiro are being transferred to the Special Investigations Unit, which is unofficially called Unit Zero because of the lack of expectations. They are paired, much to Tashiro's dislike. Their first case is a serial bomber who targets unoccupied warehouses. Yamashita figures out how the bomber is picking his targets through ramen shop ranking. They immediately head for the next shop on the list and find a possible target building. Disregarding orders, they enter the building and lose the suspect while chasing him. However, Tashiro sees a tattoo on the man's arm, and that leads them to a suspect, who isn't the bomber but gives them a clue, which leads them to the bomber.