The Reverberation of the Stars: Oath of the Sky

I used to be a maintenance worker under the stars, until I accidentally became the owner of the only intelligent mecha. That day, mankind's strongest hero burned up in front of my eyes. And I, a young man who had never even flown a fighter plane, was forced to hold on to my last hope of saving him. I became the new "sky". A legendary team that had lost its soul was forced to open up to me - the stern adjutant, the girl who laughed to cover up her pain, the silent guardian, the aloof sniper, the rich spender, the ghost who controlled the information, and the dark green-haired doctor who always repaired everything in silence. We are all different, but we share the same scars. Nowadays, a mysterious alien race tears apart the star sea and comes. Behind their invasion lies the secret of annihilating ancient civilizations. And deep inside the mecha I am driving, the whispers of AI are revealing truths that humans have never known. This is not a heroic legend of one man. This is a group of scarred people who light an oath called "guarding" for each other at the edge of the universe. Who are we fighting for? What exactly are we protecting?