Time Passes and the Immortal Guest

I was born in this era, but I do not belong to this era. I am a bystander on the chariot and a recorder of history. He took me as his disciple and taught me how to stop killing, but he made me watch him kill and then watch him die. I came to the Warring States Period and wanted to change the outcome of history. Later I discovered that the chariot of history never stops for anyone.