Do Your Best, Natsumi!.Ban and Ginji go to the beach, supposedly on a business trip, though it seems to be a vacation trip. Meanwhile in the Honky Tonk cafe, an old woman shows up, asking to retrieve a memento of her deceased husband. She explains to Natsumi that she hid her memento in her house from her son, as it was embarrassing to display it. She lost it, and had moved in with her son in his house. She had sold her house to a group of jewel thieves, later recognized, who disregard her presence from time to time, as they ignore her story about the memento. Natsumi decides to accept the case, and Paul is in shock. Natsumi makes her way to Madoka's house, but is disappointed that Shido wasn't there with her. However, she spots Emishi in the backyard, and enlists him in this recover service mission. They arrive at the old woman's sold house, failing at many attempts to get inside. As Natsumi uses various disguises to get inside the house, Emishi eventually joins in the fun. After that doesn't work out, Natsumi and Emishi decide to camp out in front of the house, waiting for the right time to sneak in. Natsumi tells Emishi about the kitty key chain that Ban and Ginji recovered for her, as it is like a memento to her. Emishi runs off to a convenience store to buy food for the two of them, while Natsumi sees that the jewel thieves leave the house. Later in the evening, after being impatient for Emishi, she runs into the house, but is caught by the trap of the jewel thieves. While the jewel thieves argue who would kill her, Natsumi makes her escape. Using her ping-pong skills, she manages to catch them off guard. She yells out for Emishi, but is stopped by the jewel thieves. However, Emishi and Kazuki make their entrance, defeating them. It is revealed that the memento to the old woman was a collection of love letters written by her deceased husband.