In episode 11 Kino shows her backstory. (I'll try my best not to spoil but still try to answer your question.)
Basically, Kino was living in a corrupt country. A traveler came along and she made friends with him. In Kino's society, once a child turned the age of 12, they were given surgery on the brain to take out the "child" in them. You could say they were brainwashed. The traveler explained to Kino how he thought this was wrong.
Kino didn't have a name at the time, so she was reffered to as "daughter", or "girl". The traveler's name was Kino. Female Kino told her brainwashed "parents" that she didn't want to go through with the surgery. He parents yelled at her and her father decided to kill her.
There was no rules against killing Female Kino, since she was believed to be her parents' property. He father dragged her out to the Male Kino, also known as the traveler, and scolded him for putting the thought in Female Kino's mind. As the father was about to murder Female Kino, Male Kino jumped in front of the knife and sacrificed himself.
Then, the motorbike started talking. Keep in mind the bike didn't talk until the traveler died. The bike had the same voice as the traveler. The bike then saved Female Kino from the corrupt society. He named Female Kino from "girl" to "Kino". The motorbike then told Kino to call him Hermes. So, basically, the bike is possessed by Male Kino.