The female characters all gain weight and join a "fasting" camp at a temple to shed it off!
A languid Kagura feels like she caught an illness, however, her body reveals that she's simply became obese. Figuring that Kagura is sick, Gintoki tries to take Kagura to the hospital, but falls through the floor due to her weight. Kagura laments over her new size and seeks advice to lose weight from Otae. Otae suggests a diet food brand known as "Bargain Dash". As she elaborates on the product, it's shown that she's put on an immense amount of weight as well. Sarutobi appears from the ceiling and disparages the two's weight problem only to crash down and reveal her own weight predicament.
Afterward, the three girls join a place known as a Diet Dojo. Otae notes that not many people survive the diet regimens held at the dojo due to its arduousness. The girls also see that Otose, Catherine, and Kyuubei are at the dojo for their own personal reasons. The head Nun then makes her appearance and has the ladies spit into a mirror to say goodbye to their repulsive self. The nun goes around and allowing each woman to spit into the mirror. When it's Otae's turn she spits on the Nun, Sarutobi lashes at the Nun, and Kagura's spit sends the nun flying backward.
Eventually, the nun passes around a single potato chip to every one that acts as the person's lifeline. If their potato chip is eaten then they're expelled from the dojo. Also humoring Kagura's request, they're allowed to eat whatever flavor they so choose. In Kagura's monologue, half of the participants drop out and 5 days later more nearly the other remaining half left. The ones remaining were Kagura, Otae, Kyuubei, Sarutobi, Catherine, and Otose. In the five days, not a single potato chip passed their lips, forcing them to rely on their cultivated "Iron Will". In the remaining time, the group cultivated strong bonds with one another while they perform their cleaning tasks around the dojo.
To break the "Gian" atmosphere, Kagura sets up a trap with her potato chip. She watches from a safe distance and in her reconnaissance, she sees Catherine in the distance. However, Kagura believes that this is just a diversion as she's in cahoots with Otose. Which is soon confirmed as Otose appears to steal Kagura's chip. Their successful ambush, however, is short-lived as Otae and Kyubei manages to steal back Kagura chip but also steals theirs. Trying to flee the scene, Kagura gets trapped in natto. A trap that was set up by Sarutobi, who was in cahoots with Otose and Catherine. Sarutobi and Kyuubei try and grab the chips off the ground. Sarutobi is convinced she has the advantage as Kyuubei's weight is a cumbersome flaw that she's not used too. Still, Kyubei manages to snap the chips and reveals that she's not fat whatsoever as she was merely doing some weight training.
Perturbed and due to losing her glasses, Sarutobi entraps everyone in a natto trap. So left with no alternative, the group each eat each other's potato chip. Unbeknownst to them, the chips were laced with a potent laxative. That evening, the head nun gloats how lucrative the diet dojo business is. Her assistant also reveals that 6 people have managed to pass the dojo trial. The news astonishes the nun and the 6 people who passed all now have gaunt and emaciated looks.
- Sakata Gintoki (minor appearance)
- Shimura Shinpachi (minor appearance)
- Sadaharu (minor appearance)
- Shimura Tae
- Sarutobi Ayame
- Yagyuu Kyuubei
- Toujou Ayumu (cameo)
- Otae is parodying Doraemon.
- "Gian" is Goda Takeshi of Doraemon. In the movie, he helps out his friends when they are in trouble, unlike his usual image of being a bully.
- This line is said by Gon in the Hunter x Hunter series.