Oguma is the main antagonist from the PlayStation 2 Metal Slug 3D.
Oguma is the CEO of the Oguma Corporation, a powerful and technologically advanced company that has obtained fame through various useful gadgets. He allies himself with General Morden to decipher a treasure that the general found 10 years before the game begins. This mysterious device is known as the Alator and it's capable of creating destructive weapons superior to anything else on the earth.
Near the end of the game, Oguma betrays Morden by "taking back" the Alator. He reveals to Marco and company that he is actually a member of the Tuatha de Danann, an advanced race of beings that live in an age three hundred million years in the past. They placed the Alator on earth three hundred million years ago as an information gathering device and intend to bring it back with them to the past. With the Alator, they intend to continue evolving their culture and erase the current timeline for their ideal history.
Once his race reaches their evolutionary peak, it inevitably self-destructs. To prevent this, they began their experiment by placing an Alator on a planet. The Tuatha de Danann sleep for three hundred million years and awake to retrieve the gathered information. If the world they examined clashes too much with their history, they will simply erase the world's current history and start the experiment over. Oguma states that they have repeated the same experiment countless times before and have recorded each instance to avoid his race's evolutionary self-destruction. Later, Marco and company believe that Oguma's experiments have caused an open rift in the space-time continuum.
He unlocks the Alator and it erects the tower giant, Lugus. While he transfers the information from Lugus to their records, the four heroes stand against them to save their history. After they defeat Lugus, another tower giant from one of Oguma's previous experiment (Lieu) absorbs it. When this happens, his culture's collected data is erased and he is forced to tame the wild new creation. Marco and his crew decide to destroy it to prevent anymore damage to the world's timeline. In spite of their efforts, the Tuaha de Dunan fail to control it and prepare to meet their final end. Before his apparent demise, Oguma flashes a brief knowing smile to the player just before he is engulfed by the living weapon.
However, Oguma manages to survive and is last seen approaching Rumi Aikawa. Expressing his sincere hope that her people may yet be able to learn from the mistakes of his, Oguma leaves the data disc of his people's history with her. Oguma is last seen turning around and calmly walking away.
Composed and wizened, Oguma is a polite scientist. He believes his actions are part of a large experiment that shouldn't be interrupted. In the end, he eventually believes in the power of humanity, partially due to Marco insisting that he lives for the future.