In the hollow Mysterious Planet, seven kingdoms co-exist, all of them lit by the Sun's Blessing from the Kingdom of the Sun, in the middle of the planet. The light of the core sun is necessary for the continued existence of all the kingdoms. Yet, something is causing the Sun's Blessing to weaken. If something isn't done, it will be the end of life in the Mysterious Planet. Fortunately, the twin princesses of the Sun Kingdom, Fine and Rein, have been endowed with the magic of the Prominence, and are looking for a way to fix things. (Source: ANN)

Black Jack is an "unregistered" doctor with a clouded, mysterious past. He works with his little assistant Pinoko (who has a massive crush on the doctor), dealing with medical cases not very well known, which can be strange, dangerous, or not known at all. But he is a genius, and can save almost any of his patients' life (as long as they have the money for it, that is), and is known to many around the world, especially to those of medicine and science. He's a man of science himself, and does not believe much until he has seen it, yet it is many times he is surprised by love and nature often overpowering the science he bases his life in.

In the year of 20XX, a young boy by the name of Netto Hikari receives a very special gift as he enters the 5th grade. His very own customized net navi, Rockman! Despite Rockman's small size and far more responsible personality, the two boys quickly become the best of friends. A net navi is designed to guide his operator from the inside of his or her PErsonal Terminal, or simply PET for short. Children and adults alike enjoy friendly "Net Battles", where they spar their navis against each other to prove their worth.

In the Edo or Tokugawa period (1600–1868), Ran, a female wandering samurai whose skill with the katana is only matched by her taste for sake (rice wine), is joined by a chinese martial artist who calls herself Lady Meow of the Iron Cat Fist. Tsukikage Ran has individual episodes that are just short stories of their adventures.