Kihei Senki Legacies

Kisshou City is one of the last habitable places in a world ruined by war. The people there gather and rebuild broken humanoid weapons known as "Legacies." When a group of bandits tries to take these weapons for themselves, the mayor uses a preserved robot named Ω99 to stop them. A teenager named Yamato is chosen to pilot the machine, despite knowing nothing about the city's troubles and being more familiar with video games than combat.