The setting of a solar system war is a familiar setting, that’s been explored in various stories. Stories From Sol: The Gun Dog is a visual novel set in a universe where such a war has concluded.
The allied front of the Martian Territories and the Jovian Unified Colony Fleet has defeated the oppressive Earth-based Solar Federation.
Your character is a Jovian, meant to take part in a battle during the final days of the war, but your mech had engineering issues.
Those issues lead to almost all of your squadron getting killed.The story of Stories From Sol: The Gun Dog opens aboard the Jovian Carrier JFS Kalyke.
Your character, who you can name, is a fresh conscript who is trained as a pilot, but training has all been done in simulations and not in real-world situations.