Eighteen years ago the planet Nebula was attacked by the Lone Star System, arch enemy of the Interplanetary Federation. Its population decimated, the few survivors swore to protect its future with their lives. That time has come. Docked in the space portal of the planet Nebula, sits the combat weapon fortress Plealos, mother ship of the Lone System's fleet. What she can't take, she'll destroy. Now's your opportunity to use your sophisticated combat skills and save your planet. You're Ryder Jupiter. Known as Ace to the Federation, you've got vengeance on your mind. And the only person you trust in battle is the faithful Diana Rean, a bold determined comrade. What brings you together is the tyrant Reficul, Emperor of Lone. His plans to dominate Nebula can only be thwarted with the power of Thunder Force II which must be jettison deep below the planet's surface to Plealos for the final confrontation. Here you'll rely on the molecular Excelizer, a blast so strong it leaves nothing behind but memories. Go forth brave one, and free the entire Federation of Reficul forever.