My Stepmom's Daughter Is My Ex

As punishment for the underwear incident, Mizuto demands Yume go on a date with him. Yume is taken aback by the sudden development, but little did she know that it was all part of Kawanami Kogure's devious plan, a plan to shatter Minami Akatsuki's delusional dreams of marrying Mizuto only to become Yume's doting little sister. And how else to do it but to show her that Yume only has eyes for Mizuto?