Vixen 357 is a strategy game developed Opus and Nippon Computer Systems (NCS) and published by Masaya. It was only released in Japan. This video shows an English fan translation of the game.

In the year 2384, aliens attacked Earth and mankind managed to win, although barely. The victory was secured by the development of of giant mechs called SERDs. After the war, all nations on Earth took part in an arms race to further develop battle mechs. A new type of battlemech called VECTOR was developed. The nation of Merisma Harp is at the forefront of development, and has established a special task force called "Slash". One day, when the Slash team is returning from a test, their base gets attacked by an army of unknown mechs.