The Technology Expo, often abbreviated as simply The Tech Expo, is an event that takes place in Lastation every four years. Various companies showcase new technologies under a common theme. It's for people to network, or exchange information and skills. The best item gets a trophy from Lastation's CPU. The theme of the the Expo is normally decided the year of the event which disables people from getting a head-start up on other companies.
The Tech Expo serves as Chian's only chance to save her shop and stop the conglomerate known as Avenir in Lastation. She requests that Neptune, Compa, and IF assist her in transporting the necessary materials for what she plans to showcase there. With the theme being weaponry, she creates a sword dubbed with the name Mech Sword Armas.
In the middle of preparing for the Tech Expo, a public broadcast from the Basilicom states that the Expo has been canceled. This makes Chian fall into a depression. The girls decide to give her some time alone, and find out that the Expo has been reopened from one of Avenir's employees, Ganache. He also states that what Avenir is planning for the Expo is something that has been in the preparation stages for three years.
The girls report back to Chian to tell her the news, and a public broadcast from the Basilicom confirms Ganache's statement to be true. However, this time it is under Parliament sponsorship. Ganache's comment about Avenir's product to be showcased at the Expo, leads her to believe that Avenir was the one who forced their hand into deciding the theme to be weaponry was Avenir themselves.
On the day of the Technology Expo, the girls raid Avenir's headquarters only to find Ganahce there instead of Singe, who is the head of the company. Ganache reveals himself to be the founder of Avenir and reveals that he had carefully manipulated everything from the start. He states that the weapon made by Avenir for the Expo, was actually meant to defeat Neptune and that if they don't get to the Expo in time, something regrettable will happen to those attending it.
Neptune and her companions rush to the Tech Expo where they meet up with Chian. Chian gives Neptune the completed Mech Sword Armas to use against Avenir's Killachine as an act of demonstration on how powerful a man-made weapon can be. The girls win using Chian's sword which marks the end of Avenir and Chian's victory in the Tech Expo.