Complex sentence: Kyosuke is still haunted by that devastating crash that occurred on the Expressway a few years ago, which caused him to leave street racing and asked Yusuke to quit street racing in which the later told him that beating his record was the only thing for him.
Split into simpler sentences: Kyosuke is still haunted by that devastating crash that occurred on the Expressway a few years ago, which caused him to leave street racing. After witnessing this, Kyousuke asked Yusuke to quit street racing in which the later replied that beating his record was the only thing for him.