Sengoku jidai

The was an unstable period of time in Japan from about the 15th century to the 17th century in which political, social and military unrest was common place. It was a time of war and chaos. The main story takes place around 1497, 500 years before the modern era of Kagome's time.

Explanation of Time Travel
The modern time is "-X-", a period in the Sengoku jidai is "-Y-", and 50 years before -Y- is "-Z-". At -Z-, Kikyo dies soon after sealing Inuyasha to the Goshinboku tree, causing him to go into suspended animation. She is then cremated with the jewel. 50 years pass and the story takes place at -Y-, where Inuyasha is still in suspended animation. At -X-, Kagome Higurashi, the 20th century reincarnation of Kikyo, is pulled into the Bone-Eater's Well bringing the jewel embedded in her body with her. She ends up at -Y- where she frees Inuyasha and they start their journey together.