In the year 2050, thirty young cartoon characters win a free copy of the latest VRMMORPG, Weapon Fantasy (ウェポンファンタジー, Uepon Fantajī). Hopper the Frog, who goes by the nickname "Kero", is one of those winners. Using a virtual reality helmet with nerve control (the ability for the helmet to control all five senses), the users must complete all fifty levels before reaching the final boss. It is possible to save the game and log out at any time. However, if a player loses the game, the user is then erased (literally) from existance. If Kero has to win the game, he and his guild must survive, or it will be game over for them.
- Hopper the Frog (ホッパー·ザ·フロッグ, Hoppā za Furoggu), nickname "Kero" (ケロ), is the main protagonist, age 17. He is one of thirty lucky cartoon characters to receive a free copy of the latest VRMMORPG, Weapon Fantasy. He has chosen to be a Paladin. Voiced by Rica Matsumoto in the Japanese version and Scott Weinger in English.
- Digger the Meerkat (ディガー·ザ·ミーアキャット, Digā za Mīakyatto), nickname "Horu" (ホル), is the deuteragonist, age 17. She is also one of the thirty to win a free copy of Weapon Fantasy. She has chosen to be an enchantress. She is Kero's best friend. Voiced by Megumi Toyoguchi in the Japanese version and Linda Larkin in English.
- Billy Bobcat (ビリー·ボブキャット, Birī Bobukyatto), nickname "Gao" (ガオ), is the tritagonist, age 45. He is one of the staff members who worked on, and is a programmer of Weapon Fantasy. He has chosen to be a Hunter. He mentors both Kero and Horu, since, in real life, he has taught them both in High School. Voiced by Shin'ichirō Miki in the Japanese version and Jim Cummings in English.