Oh My Goddess! also known as Ah! My Goddess, is a seinen manga series by Kosuke Fujishima currently serialised in Kodansha’s monthly Afternoon magazine. It was first published in 1988-08-25 (September issue). Originally a typical magical girlfriend romantic comedy, over time it has grown to feature more action and the latest variant has had a greater focus on developing the mystical aspects of the world in which it is set.
The Story
The manga tells the story of college freshman Keiichi Morisato, who, because of his pure heart, has been chosen by Yggdrasil, Heaven’s computer system, to receive a single wish. The "angelic" goddess Belldandy is sent down to Earth to ask for his wish, and tells him that he can potentially wish for anything that he wants, from becoming a billionaire to destroying the world in an instant. Keiichi first thinks that this entire meeting is a prank set up by his senpais, but during their short meeting, he soon realizes that she’s the only person who truly understands and appreciates him. Being enchanted by her, Keiichi wishes that someone like Belldandy would stay with him forever, under the condition that the offer is valid. Ironically, he does not fully comprehend the outcome of his wish, and is stunned on realizing that Belldandy will now be living with him. The manga/anime follows their relationship as they become closer to each other.
The varying anime series feature the main characters and are based on the same basic plotline as the original manga, but each has taken a unique interpretation on this concept — described below — and, as such, should be considered separate canons. The only exception to this is the more recent TV series, which follows the plot of the manga closely.
Being a mechanical otaku himself, Fujishima frequently bases whole chapters, or even story arcs, around mechanics, focusing especially on motorcycle mechanics. Most notably, readers discover that Keiichi Morisato is a member of his college’s motor vehicle club, which is always under threat of being put out of commission by a rival motor club. There are also several story arcs related to racing found earlier in the manga; the concept of racing is also a significant plot device in each of the anime canons. Both Keiichi and Belldandy are exceptionally gifted at racing (Keiichi because of natural ability and Belldandy because of her ability to "talk" with the machines). Most of the other main characters have exhibited some degree of skill in racing and/or mechanics, making the idea of mechanics a significant device for character development and growth.

