Complex sentence: In the novels she is only mentioned in passing and does not go to the Twelve Kingdoms but remains in Hourai (Japan); instead, she serves as a plot device to show Youko's lack of resistance to peer pressure.
Split into simpler sentences: In the novels, she is only mentioned in passing and does not go to the Twelve Kingdoms but remains in Hourai (Japan). Instead, she serves as a plot device to show Youko's lack of resistance to peer pressure.