Inspired by her grandfather's stories, young Shinko embarks on wild flights of fancy about the history of the little town she lives in. But dreams can't fend off the realities of growing up.

Story begins when Koala asks Butt Detective to find a missing relative who disappeared from an idol contest. The case takes Butt Detective to Stardust Island, the site of the contest, and also the home of the international criminal organization Phantom Thief Academy, headed by Phantom Thief G. Here, the organization advances its secret conspiracy, codenamed the Dark Age Plan. Butt Detective enters Stardust Island under the guise of an idol. At the same time, he joins forces with Phantom Thief U, who is out to steal back the valuable Moonlight Stone from Phantom Thief G. The story will also reveal more about Brown's past.

The Case of the Courageous Curry. On a sunny afternoon, Butt Detective and his assistant Brown are enjoying a leisurely afternoon tea at the cafe. Mr. Walter, the manager of a new curry restaurant in town, walked in with a large shopping bag. At this time, he found that the spices he had just bought, “Piriritokikku", an essential spice for curry dishes, had disappeared from his shopping bag. “You can't make curry without the spices! There is no way to open the business on schedule!” While Mr. Walter was devastated and distressed, Butt detective step forward, his remarkable reasoning mind is ready to solve the disappearance of the curry spices.