Layton Mystery Tanteisha: Katori no Nazotoki File (Layton Mystery Detective Agency: Kat's Mystery Solving Files) takes place during the events of 'Layton's Mystery Journey: Katrielle and the Millionaires' Conspiracy'.。父母失踪的秦立，在得到神秘老人的秘传功法后，开始了十年缄口修炼。与楚清音结婚后，二人尝尽人间冷暖，十年功成后，秦立开始逆袭之路！。