Long, long ago, there existed a world of magic and science. God, afraid of man's potential, split the world in to the world of science, Elde, and the world of magic, Fandavale. One day in Fandavale, a terrible witch named Cendrillon (Cinderella) revives. Cendrillon plots to rule both worlds, and searches for the "key" which holds tremendous power. A young boy from Elde by the name of Sōta meets a mysterious girl from Fandavale, Akazukin, and her talking wolf companion, Val. Sōta learns that he is the key Cendrillon is searching for. Now it is up to Akazukin, Val, and the other Fairy Musketeers to protect Sōta from Cendrillon and her Nightmarelians who wish to obtain the power he mysteriously possesses.

In a dark corner of the universe, intergalactic criminal Kain breaks out of prison and destroys the Galaxy Police Headquarters. Basking in the afterglow of the terror and destruction he has caused, Kain sets his sights toward a much bigger prize waiting on Earth. Meanwhile, Tenchi Masaki and his crew are watching some old home videos of his mother, Achika. As the film rolls, Achika slowly starts to vanish. While watching her fade away, Tenchi also begins to disappear. However, thanks to a device created by Washuu Hakubi, Tenchi is not gone for good. The gang soon learns about Kain and deduce that he must have done something to Achika, which has resulted in time being altered. To save himself and maintain the future, Tenchi travels with the girls back in time to protect his mother from her fate.

A courageous young man tries to find the only person who can save his planet from the most terrifying beast in the universe—the great white whale Moby Dick—in this futuristic anime adventure set in 4699. But locating the outlaw Captain Ahab and his illusory crew of whale hunters and persuading them to put an end to the leviathan's long reign of terror won't be easy. Will Ahab take up the challenge one more time?

Fourth season of Yatogame-chan Kansatsu Nikki.