Intro. Introduction: Yume Irido Yume is the heroine of this story. She was a girl who had been dating Irido Mizuto in junior high school, and the relationship at that time was simple, and she was a rather shy and introverted girl who was in a book. 💔 Turning point: Breakup Yume and Mizuto's relationship ends in Breakup During the middle school graduation, due to miscommunication and changes in feelings. This makes happiness become frustration with each other. 🏠 Reunion: Half-Blood Brothers But then fate played a joke! It wasn't long before she entered high school. Yume's mother (Yuni) remarries Mizuto's father (Mineaki), forcing Yume (who changed to the surname Irido after her stepfather) to return under the same roof as her ex-boyfriend as half-siblings. 📜 Current role: Competing as an "older sister" For the comfort of their parents, the two agree to set up a "fraternity rule" , with the bet that " whoever starts thinking about the other in an adulterous way will lose and follow the other's orders.