Metal Gear Solid: Lunacy of Legion

If you're not familiar with the story of Metal Gear, here's a short title-by-title explanation.

Metal Gear
The rookie soldier Solid Snake of the special ops-unit FoxHound is dispatched to enemy territory.
There he discovers the development of a nuclear-equipped, walking battle tank, Metal Gear.
He destroys it and stops the enemy plans.

Metal Gear 2
Solid Snake is again sent on a mission, this time to save a missing researcher in a nation called Outer Heaven.
He then finds out a new Metal Gear has been built and a former friend of FoxHound has turned traitor.
Snake manages to destroy this new Metal Gear and once again foil the enemy plans.

Metal Gear Solid
Sometime later, Snake has taken an early retirement. But he is dragged back into action when a break-out
group from FoxHound has taken over a nuclear disposal facility in Alaska along with some important people.
While there, Snake encounters Hal Emmerich "Otacon". An engineer forced to work on another type of Metal Gear that is under
development. He takes down the FoxHound group and stops Metal Gear once again.

Metal Gear Solid 2
Snake has left FoxHound and is now working together with Otacon in a group called Philanthropy - an anti-Metal Gear organization
that was formed to stop this mass-development of Metal Gears.
He infiltrates a facility called "Big Shell" and with the help of another guy named Raiden, he manages to set stop for another Metal Gear that's on the rise.

Metal Gear Solid: Lunacy of Legion
Why don't you go and find out?