Ema Hinata, the daughter of an internationally known adventurer, learns that her father is remarrying a successful clothing designer named Miwa Asahina. Not wanting to intrude on the newlyweds, Ema decides to move into the Sunrise Residence, a luxury apartment complex owned by her new stepmother. There she discovers that Miwa has thirteen sons, ranging in age from ten to thirty-one, all living under the same roof. Ema’s sincere hope is to build a warm, loving family with her new stepbrothers, but her sudden arrival in an all-male household immediately stirs discord. As she begins to interact with the brothers, their initial surprise and wariness gradually give way to deeper feelings. One by one, the brothers develop romantic attractions toward Ema, and what was meant to be a peaceful family arrangement becomes a tangled web of forbidden romance. The series follows Ema as she navigates school, daily life, and the escalating emotional tensions among the brothers, each of whom has a distinct profession and personality, from a responsible doctor to a rebellious musician and a stoic monk. Key narrative arcs include the shocking “first conflict” that reveals the brothers’ suspicions and protectiveness, an eventful summer vacation that brings everyone closer together, and a night when the brothers care for a sick Ema, highlighting their developing tenderness. Over the course of seven volumes, the story explores the delicate balance between familial bonds and romantic rivalry, with Ema caught at the center of a situation where every brother competes for her affection while she struggles to preserve the family unity she originally sought.