The story begins one morning shortly after the Lupin gang has moved into a new hideout in Riquewihr, France. Jigen tells Lupin that the hideout's toilet is broken. Something is clogging the drainpipe. Lupin and Jigen fight over the right to use the only other toilet in Jigen's room. There is a rule in this hideout that "you must disguise yourself as an old person when leaving your room," so Lupin quickly disguises himself and uses the toilet first. When Goemon goes out for lunch, Lupin gives him a ribbon for his role as the "old man's granddaughter," but he ends up leaving in his usual clothes anyway. However, Goemon, who was expecting Japanese food, returns disappointed after finding only buckwheat galettes. As Lupin and Jigen fight over the toilet again, Fujiko appears in the hallway. Lupin asks when she arrived, and she replies, "Yesterday, because you were drunk." Fujiko seems to know the cause of the toilet malfunction; she interrupts a call from a plumber on Lupin's phone, insisting they shouldn't let strangers into the hideout. Lupin and the others sense she's hiding something, and Lupin specifically suspects she hid something in the toilet tank. Goemon tries to confront her directly, but Fujiko pins him to the wall while nearly naked, claiming she's hiding nothing. Fujiko won't let the men near the toilet, seemingly because she hasn't recovered the "item" yet. Meanwhile, Goemon starts making soba with buckwheat flour given to him by a cafe owner. Fujiko seems to be looking for something "long and thin" to fix the clog, but Goemon refuses to help, holding a grudge because Lupin once used his chopsticks to clear a toilet clog. Lupin confronts Fujiko about the hidden "item." He tells her, "If it's important, I'll protect it; if it's dangerous, we'll fight together." Fujiko seems moved by his words but says nothing. When Fujiko pleads that she needs to use the restroom, Jigen agrees to take her. With teary eyes, she says, "Please," surprising Lupin and Goemon with her rare vulnerability. Fujiko sneaks into the toilet from the outside along the wall, reaches into the tank, and retrieves the "item." Lupin finds a "wet package" on the table, but not realizing it's Fujiko's "item," he throws it in the trash. Outside the hideout, Fujiko recalls the previous night. Because Lupin was drunk, he didn't remember when she asked about their anniversary. It's revealed that Fujiko threw Lupin's gift into the toilet tank, causing the whole mess. Fujiko mutters "Idiot" and retrieves the gift Lupin threw away from the trash can.