Mayumi Dojima gazes at the stars from the rooftop of Yubiwa Academy Middle School. She has been searching for a star that she saw in the night sky ten years ago. She meets a mysterious and beautiful boy named Manabu Sotoin who suddenly takes her to the headquarters of the Pretty Boy Detective Club, where she meets five pretty boys with unique personalities. She asks the Pretty Boy Detective Club to search for the lost star but...

The members of the Pretty Boy Detective Club: Manabu Sotoin, Nagahiro Sakiguchi, Michiru Fukuroi, Hyota Ashikaga, and Sosaku Yubiwa, along with Mayumi Dojima, visit the location where she saw the lost star ten years ago. The deadline imposed by her parents to stop searching for the star is quickly approaching. Meanwhile, she finds herself being tailed by a shadowy figure! She escapes from its evil clutches only to be told a shocking truth from the Pretty Boy Detective Club...

On their way home from school, Mayumi Dojima and Manabu Sotoin are abducted by a group that call themselves the Twenties. They are after a secret hidden within the star that Mayumi saw ten years ago. The remaining members of the Pretty Boy Detective Club take action to save their friends and finally face the Twenties in a battle! What will Mayumi's decision be after the search for the missing star ends?

The Pretty Boy Detective Club obtains an invitation to a mysterious casino called Reasonable Doubt. When they arrive at the casino, they find that all the patrons and employees appear to be middle school kids. The manager of the casino, Lai Fudatsuki, challenges Nagahiro Sakiguchi to a showdown, and if Nagahiro wins, he acquires the right to operate the casino!

Nagahiro loses to Lai, but the Pretty Boy Detective Club figures out the trick that Lai used to win. In order to battle Lai again, they sneak into the Reasonable Doubt Casino. But at the moment of the showdown, the detectives are met with an unexpected situation! What will be the outcome of the battle between the rival middle schools?