Simplify the following text for a Grade 9 native English-speaking person.
Original: Jien records that KÅ gen was the eldest son of Emperor KÅ rei , and that he ruled from the palace of Sakaihara-no-miya at Karu in what will come to be known as Yamato province .
Simplified: The GukanshÅ records that KÅ gen ruled from the palace of Sakaihara-no-miya at Karu in what will come to be known as Yamato province .