Complex sentence: He met Jyūsan-hime when he was 11 years old, shortly after Jyūsan-hime's mother was murdered by his own father, he had been sent to the house to kill her but could not bring himself to do so.
Split into simpler sentences: He met Jyūsan-hime when he was eleven years old, shortly after Jyūsan-hime's mother was murdered by his own father. Jin had been sent to the house to kill her but could not bring himself to do so.