The Legendary Mr. Y, Reborn as "Mecha Yuki" After His Acid Incident!?

There was once a soldier who defended the Earth valiantly against the Invaders until he was defeated. Half of his body was covered in lethal acid before he spoke his final word. Who was this word meant for? His family? A friend? Or perhaps, a lover? No...he must have been speaking to the soldiers entrusted with the fate of the Earth.