One day, while Mr. Brown (Satoshi Tsumabuki) was seeing patients at a pet hospital as usual, a mysterious woman named Xiaofeng (Yuriko Yoshitaka) who claimed to be his sister-in-law suddenly appeared and said that his younger brother Akito (Shota Sometani) was missing. At the same time, Xiaofeng also suspected that Akito's disappearance was related to their relatives. The relatives mentioned by Xiaofeng refer to the Yagami family, where Mr. Brown's mother remarried after her widowhood. As a "drag and drop", Mr. Brown was humiliated in the Yagami family and became estranged from them after his mother died. Akito has the blood of the Yagami family and has the right to inherit a total estate worth 3 billion yen. Now that the head of the Yagami family is critically ill, Xiaofeng suspects that someone has kidnapped Akito in order to compete for the estate. Although Mr. Brown had long made up his mind not to have any contact with the Yagami family, he could not leave women in trouble alone, so he and Xiaofeng came to the Yagami family's mansion. The Yagami family's adopted son Yongma (Indigo Fujioka), who had always looked down on Mr. Brown, and other people from the Yagami family gathered here at this time. As Mr. Brown and Xiao Feng's investigation deepens, the Yagami family's dangerous actions follow one after another. During the investigation with Xiao Feng, Mr. Brown gradually becomes attracted by her indescribable charm. After noticing Mr. Brown's thoughts, the assistant of the pet hospital, Yinshan Yuanmei (played by Nakamura Yasu), reminds Mr. Brown, but...