Because It's the Product of Our Blood, Sweat, and Tears

Synopsis

While the others go to a festival in town, where they also run into Nae, Kaito helps Kona continue her search for cheaters, introducing her to Airi and telling her about the Kimijima reports. The next day, the club assembles the top and bottom halves of GunBuild-1 together, completing its construction, although Akiho worries that she has not heard from Misaki. As a large number of people come for GunBuild-1's first test run, Kaito pilots the robots and gets it to take its first steps. However, due to the outdated construction which also results in the diesel engine failing, it fails to leave an impression on the crowd, much to Akiho's dismay. (Source: Wikipedia)