Sho Shinjo made his first appearance in Battle Arena Toshinden, as an unlockable hidden character. He also appeared as an unlockable hidden character in Battle Arena Toshinden 2, and an unlockable mid-boss in Battle Arena Toshinden 3. His moveset is mostly a blend of both Eiji Shinjo and Kayin Amoh's, although his attacks are slightly more damaging and in the third game he is significantly faster.

He had trained his younger brother Eiji and his friend Kayin Amoh in swordighting, however, he eventually abandoned the pair. He then traveled the world as a lone warrior and became infamous for mercilessly defeating any other fighters rumored to have potential, among these being Kayin's father, who he killed. When the first Toshinden tournament was announced, he secretly entered the event and encountered Cupido, a woman from the Secret Society. They fell in love and eventually had a son together, named Subaru. After the events of the third tournament, where Eiji had destroyed the Organization and its leader Abel, Sho finally faced his brother and left Subaru in his care. However, he then disappeared immediately afterwards once again.

Source: Wikipedia