Kuitan

When Seiya Takano shows up at the detective agency “Holmes Agency,” he is accompanied by a large amount of freshly steamed Chinese manju. The staff members Ryosuke Noda and Kyoko Idemizu, who had been informed by the owner that the new leader was coming, were puzzled by the arrival of the gluttonous and greedy Seiya, who even carries his own “chopsticks”. Soon after, Seiya and the others head to the scene of a case that a well-known detective, Shuji Igarashi, is in charge of, since he happened to help catch a man who eats and drinks without paying. The case is a murder in Yokohama City. A man named Shoji Yamashita, who ran a real estate business, was strangled to death in his home. Seiya and the others watch over the investigation led by Momo Ogata, a female detective who seems to be a career detective. Shoji appears to have been killed by someone while eating sushi delivered from a restaurant.

The body of a Chinese restaurant owner, who had been in Japan for five years, was found strangely murdered in Yokohama port. Since the autopsy revealed undigested tofu, minced meat, green onions, chili peppers, and miso paste in the stomach, the police begin to investigate a rival Chinese restaurant, believing that the victim was killed shortly after eating mapo tofu. Seiya is also asked by Chief Yamaguchi to assist in the investigation, but he is unable to identify the restaurant that makes the bean curd that matches the contents of the victim's stomach. Meanwhile, a boy named Kindaichi who comes to visit the office is mistaken for the victim's son, and he and Ryosuke are kidnapped by the culprit.

In order to win the 5 million yen prize, Seiya and Ryosuke compete in a TV quiz show dealing with cooking. Ryosuke is very excited when he finds out that Hitomi Moriyama, his junior from school, is working behind the scenes as a food coordinator. However, during the taping of the show, the host, Itsuro Kawakami, collapses in agony. The cause is a seizure caused by an allergy to soba noodles. The eyes of those around him focus on the eyes of Itsuro, who seems to have been sexually harassed by him. Meanwhile, a large diamond on the necklace of Madame Lan, an actress appearing as a guest on the show, has disappeared.

Seiya and his friends are asked by an elderly woman, Yamada Fusae, to search for her grandson, Kohei, who has borrowed money from a loan shark and is on the run. According to Fusae's story, Kohei is trying to kill someone. Fusae stays overnight at the office and watches over the search while cheering up Seiya and the others with her signature dish. Meanwhile, Kyoko believes that Shizuo Matsumoto, the don of the money-making world, is Fusae's first love, and arranges a reunion. Fusae learns of this and begins preparing food with a smile on her face. However, Kohei's found story reveals that Fusae is trying to poison Matsumoto, who is tormenting Kohei.

A series of murders of female pastry chefs occur in Yokohama City near Valentine's Day. Seiya arrives at the scene and suspects that a cake left behind may hold the key to solving the case. On the back of the cake, there is a pattern that looks like an inverted “4” combined with a number of horizontal lines. Momo learns that the two victims are graduates of the same confectionery school, and she becomes increasingly wary, deducing that the patissier who made the cake that was left behind will be the next target of the murder. Meanwhile, Seiya watches as Kyoko makes homemade chocolates, and realizes the secret of the cake at the scene -- it was made by a pastry chef.

Seiya and his friends are asked by Nonomura Shigezo, the chairman of a restaurant chain, to find a croquette they remember eating 20 years ago. However, the Raccoon Bridge shopping district, where the croquette store Kameya used to be, has been hit hard by redevelopment, and the store has moved to a new location and is nowhere to be found. Kyoko tries to gather information via the Internet, but she begins to receive phone calls threatening to stop her search for the croquette store, and she begins to receive unwanted phone calls. After consulting Momo and Igarashi, Seiya and Ryosuke learn that there was an incident 20 years ago in which a man fell to his death in the Raccoon Bridge shopping district, and that Kameya was involved.