From the fictional location of Domino City, Japan, Seto Kaiba took control of his adoptive father's weapons company, KaibaCorp, and dismantled it to restructure the company into something that could never be used for war.
Being skilled at programming, Kaiba's new direction for the company was gaming tech. Now he acts as CEO of KaibaCorp alongside younger brother and Vice President Mokuba Kaiba.
Subsequent business ventures included building a series of theme parks and founding a school. The main imagery of the theme parks are dragon inspired.
He's possibly the reincarnation of an Ancient Egyptian priest, or even Set, the god of chaos. But don't talk to him about that.