Synopsis

Miki Koishikawa's parents decide to get divorced-- but no one's moving out. Instead, a second family is moving in and all the adults are switching partners. To make things more difficult, this second couple has a son Miki's age, Yuu, who annoys Miki to no end while also being strangely attractive. In addition to these domestic troubles, Miki faces a new conflict with her best male friend and long-time crush, Ginta, and finds herself torn between an old friend and a new stepbrother.

Characters

• Miki Koishikawa - Miki is a fairly normal high school girl whose parents have thrust her into a situation that is far from normal by moving in with another couple and switching around partners.
  
  
• Yuu Matsuura - Yuu is Miki's new stepbrother. His good looks make him the target of much curiosity when he begins attending Miki's high school, and he can be charming as well, but tends to keep his true feelings to himself.
  
  
• Meiko Akizuki - Meiko is Miki's best friend at Toryo High. She is fairly quiet, generally keeping her feelings to herself, much like Yuu.
  
  
• Ginta Suou - Ginta is a long-time friend of Miki's. He is also her former love interest, having rejected her two years before the outset of the Marmalade Boy series.