Genma (幻魔) made his first and only appearance in Battle Arena Toshinden 4, as an initially playable character.
For as far back as 2000 years in China, Genma has been a member of an assassin clan (rumored to be the same one as Fo Fai's), as well as being an intense researcher of sorcery. After a long time, he mastered dark magic and discovered the secret to eternal life, but doing so eliminated all emotions within him. Since he no longer had a conscience, he began to kidnap children and train them as evil murderers to do his bidding. Among these was a ninja girl named Miyabi, whom he had placed a spell on that rewrote all of her original memories.
Genma eventually killed the owner of a very powerful shield. The relic, which was known as the Genbu shield, was the same one Chaos used to carry and was one of the Four Sacred Arms, special weapons which gave tremendous power to their owners. Upon learning that there were three other weapons of its kind, he decided to seek them out for himself. After missing his chance to acquire the Seiryu spear, which used to belong to the spy Mondo, he entered the fourth Toshindaibukai with Miyabi, along with a cyborg named Bang-Boo in order to gather the Four Sacred Arms all at once.