Six months after the events in Hammer Session!, the genius swindler Otowa Yonko returns with the goal of acquiring more formidable achievements. A chanced encounter with his former partner-in-crime Mizuki sensei however, prompts him to come to Hanazono High School to help solving his fellow students' problems, using his signature Hammer Session.

Two prisoners managed to escape after the police truck carrying them crashed on the highway. One of them , Mr Sawazaki is a gangster who has sent 10 different bosses to hospital. The other called "You" - our protagonist - is a con artist whose cheating profile has piled up to approximately 100 billion yen. Accidentally, "You" then becomes the new teacher for the nearby high school, under the new name Takeda Shindo, and according to a deal of "Hammer Session" with the headmaster.