The main character of DUAL!, Kazuki is regarded as a pariah by his classmates because he periodically has visions of giant robots battling in the city. After being accidentally sent to the parallel world by Ken and Mitsuki Sanada, Kazuki discovers that he is the only male that can control the mechas. Because of his unbelievable piloting skill, he is commissioned to the Earth Defense Force and becomes the new pilot of the white Core Robot. His cover story at school is that he's Mitsuki's little brother, which gives Kazuki quite a bit of trouble.

Curiously, there is no alternate version of Kazuki Yotsuga in this world. Later in the series, Kazuki subconsciously awakens one of the original alien mechas, a robot named Zinv. It's revealed that Zinv is Kazuki's counterpart in the parallel world.

Kazuki is the stereotypical harem anime protagonist: a shy, quiet and awkward everyman possessing incredible fighting power and illogical charisma. As usual, he attracts a bevy of beautiful women.

When Zinv is destroyed, Kazuki's desire for the group to stay together results in the creation of a third possible world, where elements from the parallel universes are combined.

Interestingly, in the world of Tenchi Muyo!, Kazuki Yotsuga is the name of Tenchi's great-great-grandfather.

(Source: Wikipedia)