Zombie Zone, the first game in the Oneechanbara series, is a 3D person Action Adventure Hack and Slash game, in a similar vein as Capcom's Devil May Cry series or KOEI's Dynasty Warriors. The game has the players, as the lead character Aya, running through the streets of a desolote Tokyo, fighting hordes of the undead with her sword. The game's simple combat is augmented by the precise timing involved in hitting "cool" hit's which inflict more damage on enemies. It also features both a rage meter, which when filled sends Aya into a berserk trance, and a bloody sword meter, which represents your swords condition, and as it fills, you'll inflict less damage until, when completely full, your sword will get stuck in enemies.
Alongside the regular story mode, the game also has a survival mode, pitting the player against hordes of enemies from the story levels, including bosses, in arena style areas, with progressing difficulty as more and more stages were cleared. The game also features a number of quests, certain actions that could be fufilled during story stages to unlock extra costumes.
Sometime in the 21st century in a war-ravaged Tokyo emerged a pair of rivalrous siblings. Aya, who was raised by her father, was disciplined to master the art of the sword. However, her father was one day killed by an unkonwn being, causing Aya to vow revenge against the perpetrator. Saki, the younger sister, was raised by her mother, who eventually died from exhaustion. Furious at her father for abandoning her and her mother, Saki took out her revenge against him, fatally, and has taken it upon herself to bring her mother back to life, after discovering an ancient art that could bring the dead back to life. However, the only way this can be done is to collect the heart of her sister, Aya. Admist the madness of a zombie-ravaged Tokyo, the battle between the two sisters begins.