Osaru is the alternate final boss from Aero Fighters/Sonic Wings, and a recurring enemy in the series. Almost nothing is known about him, aside that he was created by Fata Morgana as a weapon of mass destruction.
Osaru will sometimes appear as the final boss instead of Pandora. He will appear after the Space Shuttle in the final mission is destroyed, but instead of a missile, a escape pod will come out of the wrecking shuttle, and Osaru will pop out and engage the player in battle. Much like Pandora, the battle against him is timed, so failure in stopping him will result in a bad ending where he is shown stomping a city.