It was originally broadcast on Wowow from April to July 1999 and was licensed in the US by Pioneer LDC, later known as Geneon.

In addition to the original TV run, an OVA special was added to conclude the series as a de facto "14th episode".

The title refers to the fact that the story takes place in two parallel universes, a concept loosely based on multiverse theory.

22 years ago, a huge alien artifact is found on a construction site by a worker named Yotsuga.

One day, the most popular girl in school, Mitsuki Sanada, approaches him to tell him that she likes his stories.

This is only a ruse; she lures him to her father, Dr. Ken Sanada, who wishes to study Kazuki for his research on parallel worlds.

Along with a military escort, she takes him to the Earth Defense Force HQ, a paramilitary operation led by this world's Dr. Sanada.

Later on, a new type of robot made from the artifact is deployed that can cause objects and people to be shifted between the alternate worlds.

A decision must be made; since Kazuki and the alien technology are exclusive to each world, one must be eliminated to halt the destruction.

The robots are destroyed, and the worlds combine into one, an expression of Kazuki's wish for all his (girl)friends to continue to stay together with him (even though the action is again caused by Mitsuki's carelessness).