BLACK HEAVEN starts out ordinarily enough. Oji Tanaka is your typical Japanese office worker just trying to make a living. His wife and kid ignore him, his boss is always giving him grief, but he keeps on slugging through the daily grind because it is his life (or what has become of it). But his whole word gets smashed to pieces the day his wife throws away his last guitar. You see, Oji used to be the front man Gabriel Tanaka for the rock band 'Black Heaven' fifteen years ago. And the guitar that was thrown away was not only a Flying V, which is a very expensive instrument, but it was also his last link to a time in the past when he was truly happy.

That night while Oji is out drinking, trying to forget that his most prized possession was just thrown out, he coincidentally runs into Layla Yuki, a new employee at his office. I say "coincidentally" because the whole day, while Oji was working, Layla was following him around and spying on him. Layla tells Oji that she was a big fan of Black Heaven and tells him that she can take him to "heaven." Oji, thinking that he is going to have at least a brief affair with Layla, allows her to lead him to "heaven." But instead of ending up at one of the infamous Japanese love hotels, he is instead led to one of the new model homes being shown off in his neighborhood. It is inside this house where Oji is transported to a ship in outer space and is reunited with his lost Flying V. And once Oji has his precious guitar in his hands again, Layla asks him to play and Oji happily obliges.

As it turns out, Layla is really an alien soldier fighting a war in space. Oji's guitar playing, for some reason, activates an ultimate weapon which Layla's side can use to defeat their enemies. Oji takes all of this pretty well, considering the goofiness of the whole situation. He is just happy to be playing guitar.

Layla also has another mission besides getting Oji to play his guitar. Layla has been assigned to study Oji and find out why only his guitar playing activates the ultimate weapon. Layla is aided in this assignment by three girls named Kotoko, Eriko and Rinko who know even less about Earth culture than Layla does. In fact, the three girls act more like the Three Stooges than actual soldiers.