Imoriya Mato just wants to live a quiet life at school, but she's also competitive by nature. Her friend, Kouda-chan, asks her to represent their class in the competition for the right to use the rooftop at the school festival, known as the "Fool's Smoke Game." She gets caught up in a series of unusual challenges...? Deception and logic lead to victory - the ultimate battle of wits where no one dies!

The setting is London at the end of the 19th century. A young vagrant boy, Louie, meets Sherlock Holmes, a consulting detective who has just opened his own practice, after a murder case. Despite his hatred for Holmes, who does not pay attention to cases involving anything but the upper class, Louie decides to become Holmes' "dog" and work for him in order to gain the ability to protect the homeless children.

A boy, the head of the broadcasting club, was stabbed to death by someone in the old gymnasium of Kazugaoka High School. It was right after school, raining heavily, and the scene was a locked room!　The police assume that the crime was committed by the head of the women's table tennis club, who was the only person in the gymnasium after classes ended early. Yuzuno, a member of the ping-pong club who was at the scene when the body was found, asks Tenma Urasome, who is known as the best genius in the school, to find out the truth for the suspected club leader.