Ema Hinata, a high school girl, moves into the Sunrise Residence after her father remarries the successful clothing maker Miwa Asahina. There she discovers she has thirteen stepbrothers, all living under one roof. Among them are Yusuke Asahina, a sixteen-year-old student, and Futo Asahina, a fifteen-year-old idol singer. Yusuke first meets Ema at school and is immediately drawn to her, unaware that she will soon become his stepsister. Futo, known for his musical career, also finds himself developing romantic feelings for Ema. The manga follows the perspectives of these two brothers as they each fall in love and attempt to win Ema's heart, while living together as a new blended family. The central conflict arises from the tension between brotherly loyalty and romantic desire, leading to rivalry and emotional turmoil. Key narrative arcs explore Yusuke's struggle with his feelings after learning Ema's true identity, and Futo's efforts to hide his affection while balancing his public persona. The story unfolds primarily within the Asahina household and their school, as the brothers compete for Ema's attention, even as Ema herself seeks only to build a loving family.