This game is rated PEGI: PEGI 16 for Violence.
Zombie Zone is the European localized name for the first game in the OneeChanbara series. It's a part of the Simple 2000 series by Japanese publisher D3 Publisher, as part of a series of budget priced games that usually sell at 2000¥. You play as Aya, a scantily clad cowgirl with a scarf, in a hack-and-slash against slow-moving zombies in little arena's. There is a feature called "sword fatigue": if you don't clean your sword in time, it will get stuck in an enemy, giving him an advantage over you. There are also slight RPG elements. You can upgrade your characters by collecting orbs dropped by defeated enemies. At the end of each level, you can use the orbs to make Aya more powerful. Sometimes the enemies drop red orbs; if you collect enough of them, you turn into a demon. Your attacks become more powerful, but they also take away from your health.
You control Aya, a young girl who has lived with her father. An excellent swordsman, he has left his wife and the daughter Saki to live in a secluded place, teaching Aya sword techniques. His wife died, and Saki blamed the father for her death. She killed her own father, and went off to find an artifact to resurrect her mother. Now Aya must stop her own sister and avenge her father's death.
