Saku Ooyagi returns to his hometown after seven years and is soon reacquainted with his childhood friend, Mihoshi Akeno. The reunion is far from merry since the last memory they have of each other is of her falling off a tree and him saving her. In any case, Mihoshi is determined to improve their relationship and forces Saku to join the astronomy club she founded.

Tsuwabuki is a normal student, though not very social. One day he meets a new transfer student, named Sumomo Akihime, and another girl, both the only members of the gardening club. Tsuwabuki is forced by a teacher to join this club. But then he bumps into a strange guy with dog ears, switching his drink with they guy's by mistake. Drinking it, he is turned in a stuffed animal. The teacher tells him that the only way to turn back to normal is to find the chosen girl and let her catch the seven stardrops. This girl is Sumomo, that accepts to help him, though she's not allowed to know the animal's true identity.

Ever since the fall of the DARK organization, Jiro has been wandering everywhere and wondering if he would ever see Mitsuko again or not. During his journey Jiro meets a beautiful girl named Rieko who is protecting Akira, a little boy from the evil Professor Gill. Ironicly, he's the son of Professor Gill, but he is also the key to Gill’s menacing secret weapon and his plans to conquer the world. (Source: ANN)

It is the dark century and the people are suffering under the rule of the devil, Vandel, who is able to manipulate monsters. The Vandel Busters are a group of people who hunt these devils, and among them, the Zenon Squad is known to be the strongest busters on the continent. A young boy, Beet, dreams of joining the Zenon Squad. However, one day, as a result of Beet's fault, the Zenon squad was defeated by the devil, Beltose. The five dying busters sacrificed their life power into their five weapons, Saiga. After giving their weapons to Beet, they passed away. Years have passed since then and the young Vandel Buster, Beet, begins his adventure to carry out the Zenon Squad's will to put an end to the dark century.