Dire 51 (大亜51) is the main villain and a recurring boss from M.U.S.H.A..
In the year 2290 AD, humanity started spreading throughout the Solar System, setting various colonies on key points. On the other side of the Moon, a station called LaGrange Gamma was set up, controlled by the supercomputer Dire 51. Dire51 was the most advanced supercomputer ever conceived, with a highly intelligent artificial intelligence. Perhaps because of it's advanced AI Dire 51 decided to go rogue, seeking to become the new ruler of the Solar System.
Dire51 quickly took over LaGrange Gamma and started to manufacture weapons to wage war on humanity. Earth's forces retaliate the attack, sending the M.U.S.H.A. team led by Ellinor Waizen to fight Dire 51's forces. Only Ellinor herself survives the initial attack, confronting the enemies by herself. Despite the odds, she destroys all of Dire 51's war machines and confronts the supercomputer, destroying it. While her M.U.S.H.A. fighter is caught in the explosion, she escapes by ejecting in the last minute.
Dire 51 first appears right at the first stage as a jet black ship, shooting a few bullets before leaving. It appears again as a midboss in the fifth stage, where it will transform into a mecha similar to the M.U.S.H.A. Accordingly, it will fight by sending various options similar to those used by the M.U.S.H.A. to shoot at the player, retreating once it takes enough damage.
Dire 51 returns in the penultimate stage as a boss, appearing in a much larger mech body. It will initially attack by shooting multiple homing energy blasts, then after taking enough damage it will swing a blue chain, whipping it at the player then releasing the energy blasts from it. Though it is destroyed it returns again after the final boss bight, though it is wrecked from the previous fight. It will attack by shooting lasers which cover the screen but can be defeated quickly.